Xiaohua read a story book. She read 14 pages on the first day and 20% of the whole book on the second day. At this time, the ratio of the number of pages she has read is 2:3. How many pages does the story book have in total

Xiaohua read a story book. She read 14 pages on the first day and 20% of the whole book on the second day. At this time, the ratio of the number of pages she has read is 2:3. How many pages does the story book have in total

Suppose the book has x pages
2/（2+3）x—14=20%x
2/5x-14=1/5x
5(2/5x-14)=5（1/5x）
2x-70=x
2x-70+70=x+70
2x-x=x+70-x
x=70
A: the book has 70 pages

M & # 178; - M-1 = 2, what is m equal to?
How to solve this equation
M & # 178; - M-1 = 2, what is m equal to

Solution
m²-m-1=2
m²-m=3
m²-m+1/4=3+1/4
(m-1/2)²=13/4
Prescription:
M-1 / 2 = √ 13 / 2 or M-1 / 2 = - √ 13 / 2
∴
m=1/2+√13/2
Or M = 1 / 2 - √ 13 / 2

The speed ratio of the two vehicles is 4:3. After meeting, the speed of the bus decreases by 20%,
Increase by 1 / 3, so that when the bus arrives at B, the truck is 25km away from A. Q: is ab km away?

1. The speed of the freight car is 3 (4 + 3) = 3 / 72, the speed of the passenger car is 4 (1-20%) = 3.2, the speed of the freight car is 3 (1 + 1 / 3) = 4, the distance of the freight car is (3 / 7 △ 3.2) X4 = 15 / 28 when the passenger car arrives at B, and the whole journey is 25 (4 / 7-15 / 28) = 25 (1 / 28) = 700 (km)

Log2 (x ^ 2-2x = 29) > = 5 is the value of X
Log2 (x ^ 2-2x-29) > = 5, minus sign in the middle, wrong type

∵ x^2-2x-29>0√
log2(x^2-2x-29)≥5=log2[2^5)
That is, x ^ 2-2x-29 ≤ 32
∴x1+√30,1-√62≤ x≤1+√62
The solution set of 〈 log2 (x ^ 2-2x-29) ≥ 5 is as follows:
{x:1-√62≤ x

Ask a and B two people each walk a section of road, they use the time ratio is 4:5, the speed ratio is 5:3, they walk the distance ratio is how many detailed process and analysis

According to the formula "distance = speed × time", calculate the distance of each party
The distance a takes is: 4 × 5 = 20
B: 5 × 3 = 15
Then the distance ratio of a and B is 20:15 = 4:3
A: the distance ratio is 4:3

Is the proportion with unknowns an equation? Is it right or wrong?

Wrong
An equation is an equation with unknowns
But: the proportion with unknowns is not necessarily an equation
For example, 6x: x = 12:2 is not an equation. On the surface, there is an unknown number, but in fact it is a false unknown number

Does the rocket rise by the reaction of force? If so, how does it get the reaction in the vacuum universe?

There is nothing to do with the air on the rocket! The rocket depends on the reaction force. Who gives the reaction force to the rocket? Gas (note that it is gas, not air) is the gas generated by the combustion of high-pressure fuel in the rocket engine. These gases are ejected in the opposite direction of the launch, giving the rocket a reaction in the direction of the launch

Solving the equation 3 / 7 plus x equals 4 / 5?

15 out of 35 plus x is 28 out of 35
28 out of 35 minus 15 out of 35 equals
13 out of 35 = x

Put two solid cubes A and B made of the same material on the horizontal table top, and the pressure of a and B on the table top is P1 and P2 respectively. Put a on top of B, as shown in the figure, then the pressure of B on the table top is ()
A. p1+p2B. p12+p22C. p13+p23p22D. p13+p23p12

Let the density of two cubes be ρ, and the side lengths be L A and L B respectively. The pressure of a on the table top is: P1 = g a, s a = ρ GL3 a, L2 a = ρ GL1 a, ∧ L A = P1 ρ g, similarly, l b = P2 ρ g. when a is placed on B, the pressure of B on the table top is: P = ρ GL3 a + ρ GL3 B, L2 B = ρ g (P1 ρ g) 3 + ρ g (P2 ρ g) 2 = P31 + p32p22

Find the unknown x.3.2 × 2.5-75% x = 212 ÷ (0.5x + 1) = 4 (x-1): 37 = 0.1:374x-24 = 2x + 20

（1）3.2×2.5-75%x=2               8-0.75x=2         8-0.75x+0.75x=2+0.75x                   8-2=2+0.75x-2                6÷0.75=0.75x÷0.75                     x=8（2）12÷（0.5x+1）=412÷（0.5x+1）×（0.5x+1）=4×（0.5x+1）                     12÷4=4×（0.5x+1）÷4                 0.5x+1-1=3-1                0.5x÷0.5=2÷0.5                         x=4（3）（x-1）：37=0.1：37            x-1=0.1          x-1+1=0.1+1              x=1.1（4）4x-24=2x+204x-24-2x+24=2x+20-2x+24         2x=44      2x÷2=44÷2          x=22