Solution equation: 15x + 9 = 18x-18

15x+9=18x-18
18x - 15x = 9 + 18
3x = 27
x = 27 ÷ 3
x = 9

Why is one-third of a cycle greater than 0.3, but why is a cycle of 0.3 * 3 equal to a cycle of 0.9, while one-third times three equals one
Is one third not equal to 0.3 cycle? I'm a junior high school student

9 = 1
Baidu Encyclopedia has strict proof:
Suppose x = 0.999
　　∵
　　10X = 9.999...=9+0.999... =9+x
Namely
　　9x = 9
　　∴
　　x = 1

If Mo, | m | > | n |, then M + n () 0 (fill in greater than or equal to)
If M > 0, n > 0, | M|

1.<
2.>
three point three
4.-12

The calculation: 1, (x-3y) × (- 6x) 2, (2 / 3ab-178; - 2Ab) × 1 / 2Ab 3, 2a-a-a-178; (-a-178; - 2A + 1) 4, (x-3y) × (- 6x) 2, (2 / 3AB and 178; (2 / 3AB) × 1 / 2Ab 3, 2a-a-a-178; - 2a-a-a-178; - 2a-a-a-178; - 2a-2ab) × 1 / 2Ab 3, 2a-2a-a-2b-2b-2a-2b-2a-3, 2a-2a-\\\\\\\\\\\\\\\\\\\\\\\a-b) (- 5A + 2b) 11; +In this paper, y = - 312, known x \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\y) (x + y) = x & # 178; - 2XY + Y & # 178; D. (M + 2) (3m + 6) = 3M & # 178; +6m + 12 15. The following calculation is correct: A. (2x-1) (X-2) = 2x & # 178; - 3x + 3 B. (x-3) (x + 2) = x & # 178; + X-6 C. (X-Y) (X & # 178; + XY + Y & # 178;) = x & # 179; - Y & # 179; D. (a + b) &# 178; = A & # 178; + B & # 178;

1. (x-3y) (6x-6x) × (6x-3y) × (6x) ((6x) ((6x)) ((6x)) ((6x) x (2 / 3A B \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\;) =

1ab is 3030 meters apart. A goes from a to B. after 5 seconds of departure, B goes from B to a and meets each other in 5 minutes. It is known that B's speed is 4 m / s
A and B are 285m apart and face each other. A walks 8m per second from a and B 6m per second from B. If a walks 12m first, how many seconds does a start to meet B?
The first class of grade 27 marched to Jiadi at the speed of 6 kilometers per hour. Xiao Gang arrived at the end of the team at the speed of 10 kilometers per hour and then returned to the end of the line at the same speed. It took a total of 7
3. When a ship is sailing between the two docks of AB, the known speed of water flow is 3km / h. It takes 5h for a ship to sail downstream and 7h for a ship to sail upstream. Find the distance between the two docks of ab

1. Let a velocity be x m / s
5min=300s
3030-5x=300（4+x）
3030-5x=1200+300x
1830=305x
X = 6 A: the speed is 6m / s
285-12=273
273/(8+6)=273/14s
273/14+12/8=273/14+3/2=21s
A: meet in 21s
2. 7.5 minutes = 0.125 hours
The team length is x km
x/(10-6)+x/(10+6)=0.125
x/4+x/16=0.125
(4x+x)/16=0.125
5x=1
x=0.4
A: the team is 0.4km long (400m)
3. Let the flow velocity be x km / h
(x+3)*5=(x-3)*7
5x+15=7x-21
36=2x
x=18
(3+18)*5=15+90=105(km)
A: the distance between the two places is 105km
I work so hard, give me some points!
By the way, what grade are you in? These are the Olympiad math questions for grade 4 and grade 5 of primary school. Junior middle school students usually do

Tomorrow afternoon class. Hope someone can help
OK, I'll give you the score
two
There are 200 workers in the factory, each of whom can weave 30 meters of cloth or make 6 pieces of clothes every day. Each piece of clothes needs to take 2 meters. If the clothes are sold directly, the profit per meter is 2 yuan. If the clothes are sold, the profit per piece of clothes is 25 yuan. Now x workers are arranged to make clothes. For the rest of the clothes, X means profit P.
3. Polynomial (M & sup2; - 25) x & sup3; - (M + 5) x & sup2; + X + 3 is a quadratic trinomial about X.
(1) Find the values of the following expressions.
① （m+2）（m-2）； ② m²-4
(2) What do you find from the results of questions 1 and 2?
four
Let's write this polynomial. If x and y satisfy | x + 2 | + (Y-1) & sup2; = 0, what is the value of this polynomial?
five
Given that the value of polynomial 3 (AX & sup2; + 2x-1) - (9x & sup2; + 6x-7) has nothing to do with X, try to find the value of 5A & sup2; - 2 (A & sup2; - 3A + 4).

3 because (M & sup2; - 25) x & sup3; - (M + 5) x & sup2; + X + 3 is a quadratic trinomial of X, so M & sup2; - 25 = 0, M + 5 ≠ 0, so m = 5, so (M + 2) = 7 (m-2) = 3 (M + 2) (m-2) = 21m & sup2; - 4 = 21 it is found that: (M + 2) (m-2) = M & sup2; - 4 (M + a) (M-A) = M & sup2; - A & S

1. The known integer A.B.C satisfies (20 / 3) a power × (8 / 15) B power × (9 / 16) C power = 4
Find the value of a.b.c
2. Given the m power of a = 4; n power = 8, we can calculate the 2011 power of (3n-3m power of a-33); we can't say the reason

1. (20 / 3) a power × (8 / 15) B power × (9 / 16) C power = 4 can be changed into: (20) a power / (3) a power × (8) B power / (15) B power × (9) C Power / (16) C power = 2 square [(2) 2A power × (5) a power] / (3) a power × (2) 3B power / [(3) B power × (5) B power] × (3)

Hanshan Temple rings the bell every 9 seconds. When the bell rings for the first time, ships a and B sail up and down the river at the speed of 3m / s and 9m / s respectively. When ship a hears the 108th sound, ship B can only hear the () sound. (V sound = 300m / s)

So we can calculate the time when we hear the sound of a 9 t * 108
Then we can know the distance s of ship B. then (s-300t) / 300 (round), it is the number of hours between ship B and 108. So it is 108 - (s-300t) / 300 (round)

I forgot the specific questions. I hope you can help me find the questions and analyze them, or you can directly analyze them for me. There are three questions in total. The first one has already been learned
As shown in the figure, the radius of ⊙ o OP = 6, the chord AB bisects OP vertically, intersects op with F, the moving point d different from a and B is on the arc ab. de ⊥ AB is on e, and ⊙ D is the inscribed circle of triangle ABC. (1) find the length of AB (this will find it) (2) determine whether ACB is a fixed value, if it is to find the angle, if it is not to explain the reason
Because the grade is not enough, it can't be illustrated~

(1) Connecting OA, if the intersection of OP and ab is f, then OA = 1. ∵ chord AB vertical bisector line OP, ∵ of = 12op = 12, AF = BF, in RT △ oaf, ∵ AF = oa2-of 2 = 12 - (12) 2 = 32, ∵ AB = 2AF = 3. (2) ∵ ACB is a fixed value

Three teams play a single round robin game (each team in the business game plays one game with all the other teams)
The same question, if it is 4 balls
Write out the formula of the total number of games n when m teams play a single round robin game
Why is the answer m (m-1) divided by 2

First of all, the number of teams is m, then M (m-1) is needless to say. For example, for team a and team B, team a and team B play, not only for team a and team B, but also for team B and team A. but according to 2x (2-1) = 2 (games), we need to divide it by 2, because m (m-1) is only for each match

Solution equation: 15x + 9 = 18x-18