The problem of removing bracket and denominator It takes 11 hours for a ship to arrive at a place after 9 hours downstream from a place, and it takes 11 hours to return to a place according to the original route?

Let X be the water purification velocity;
(x+2) *9 = (x-2) * 11
(11-9) * x = 2 * (9+11)
X = 40 / 2 = 20 km / h

What's the angle of the time with my watch? In fact, I don't know the title at all
a. 11 o'clock
b. It's three o'clock sharp
c. It's six o'clock sharp
d. Half past six
e. It's two forty-five
f. It's 3:24
There are five classes in a school
ABCDE.
There are 28, 31, 24, 26, 29 students
In one of the classes, there are twice as many girls as boys
Which class is it? How many girls and boys are there?
Please write down the formula when you say it~

1、
a. 11:00 30 degrees
b. Three o'clock sharp 90 degrees
c. Six o'clock sharp 180 degrees
d. Half past six 15 degrees
e. 2:45 172.5 degrees
f. 3:24 42 degrees
2、
It's class C, 16 girls and 8 boys

Two math problems, please,
A subscript n (that is, the position of the decimal point) = a subscript 1 + (n-1) d (n is a natural number), if a subscript 2 = 5 and a subscript 5 = 14 are known, then what is a subscript 10 equal to?
Although the expression is not very clear, for example: A. subscript letters and numbers are the position of
Help to write another question:
The square of (4x + Y-1) + | 2y-2x + 1 | = 0, find the value of X and Y. the absolute value of "|"

an=a1+(n-1)d
a2=a1+(2-1)d=a1+d=5
a5=a1+(5-1)d=a1+4d=14
The solution is: D = 3, A1 = 2
So: A10 = a1 + (10-1) d = 2 + 9 * 3 = 29
The square of (4x + Y-1) + | 2y-2x + 1 | = 0,
Because both the square number and the absolute value are greater than or equal to 0, if the equation holds, there are:
4x+y-1=0.[1]
2y-2x+1=0.[2]
[1]+[2]*2:
5y=-1
y=-1/5
4x=1-y=6/5
x=3/10

Division of the same base power
Nowadays, there are about 1.3 billion people in China. The per capita annual consumption of grain is 150 kg. Now the grain output per hectare is about 7500 kg. In order to achieve food self-sufficiency, how many hectares of cultivated land must China retain?

China's grain demand = 13x10 ^ 8x150 = 1.95x10 ^ 11
Hectare = 1.95x10 ^ 11 △ 7.5x10 ^ 3 = 0.26x10 ^ 8
China must retain 26 million hectares of arable land

If a ^ C = B, then (a, b) = C, for example, 2 ^ 3 = 8, if (2,8) = 3, then (3,27)=_ ,(5,1)= ,(2,1/4)=____

(3,27)=_ 3____ ,(5,1)=___ 0___ ,(2,1/4)=__ -2____

Division of the same base power
Given the area of a rectangle s = 7 ^ 5, one side a = 5 ^ 4, find the length of the other side B
Can you find the length of B on the other side?
What is your method?
Observe B = 5 ^ 7 △ 5 ^ 4 = 5 ^ 3, what is this operation? What is the relationship between indexes?
Sorry, wrong number. Area is 5 ^ 7, not 7 ^ 5

b=s/a=7^5 /5^4=2401*7/625=16807/625=26.8912
The division of the same base power is the exponential subtraction of the same base power
This problem is not the same background, so it cannot be subtracted
For 5 ^ 7 and 5 ^ 4, B = 5 ^ (7-4) = 5 ^ 3 = 125

There's a bunch of numbers, expressions and ranges
A column of numbers 3, 6, 9, 12. Take out four adjacent numbers and find the expression and range of n
The adjacent numbers are 3,6,9 and so on, not 1,2,3,4 and so on

This column of numbers is an arithmetic sequence with the first term of 3 and the tolerance of 3
General term formula an = a1 + (n-1) * 3 = 3 + (n-1) * 3 = 3N (n is greater than or equal to 1)
Four adjacent numbers can be expressed as 3N 3 (n + 1) 3 (n + 2) 3 (n + 3) n whose range is greater than or equal to 1

What are the expressions of information retrieval?

There are three kinds of Boolean logic operators in common use: logic or "or" (+) logic and "and" (*) logic, not "not" (-)
The computer will match the query with the record in the system according to the query. When the two match, it will hit and output the document record automatically

If the solution of the equation (2x + a) / (X-2) = - 1 about X is a positive number, the value range of a is obtained
I know a is less than 2, but
A is not equal to - 4?
. help... Thx
But a is not equal to - 4 GA

Solving equation (2x + a) / (X-2) = - 1
(2x+a)/(2-x)= 1
2x+a=2-x
x=(2-a)/3>0
So a

The equation (a + 2) x + (B-1) y = 3 is a quadratic equation of two variables. Try to find the value range of a and B!

Bivariate linear equation, that is, the coefficient is not equal to 0
A + 2 ≠ 0, that is, a ≠ - 2
b-1≠0,b≠1

The problem of removing bracket and denominator It takes 11 hours for a ship to arrive at a place after 9 hours downstream from a place, and it takes 11 hours to return to a place according to the original route?