Find the equation (one variable one time), and the relationship 1、 The distance between the enemy and our army is 25 km. The enemy runs away at the speed of 5 km / h. our army pursues at the speed of 8 km / h at the same time, and fights at the distance of 1 km. How many hours after the pursuit begins? 2、 A and B practice running. A is 7 meters per second, B is 6.5 kilometers per second. If B runs 8 meters first, how many seconds can a catch up with B? 3、 A pair of students had a military exercise. They were traveling at a speed of 5 km / h. after 18 minutes, the school sent a notice to the team leader. The correspondent rode a bicycle 14 km / h to catch up with the students. How many hours can he catch up with the students? 4、 It takes 25 seconds for a train to enter a 300m tunnel at a constant speed. A fixed lamp on the top of the tunnel shines vertically on the top of the train for 10 seconds. The length of the train can be calculated 5、 A circular runway is 390m long, 6m / s in a and 7m / s in B 1. How many hours have they met for the first time in running at the same time, on the same ground and in the same direction? 2. How many hours have they met for the first time? Question 2 B run 6.5km per second

1、 Let x happen after X hours, and the equation is (8-5) x = 25-1
2、 Let x seconds catch up, and the equation is (7-6.5) x = 8
3、 The equation is (14-5) x = 5 * 18 / 60
4、 Let the train length be x and the equation be (300 + x) / 25 = x / 10
5、 Let's meet for the first time in X hours. The equation of question 1 is (7-6) x * 3600 = 390
The equation is (6 + 7) x * 3600 = 390

Requires a series of equations, one variable equation
The absolute value + B = 0 of the equation (a + 1) x ^ A + 2 of X is a linear equation of one variable. We can find the value of 2A ^ 2-A / 3-A ^ 2A / 2-A ^ 2 + 5A / 6

(a + 1) x ^| a + 2 | + B = 0 is a linear equation with one variable
So a + 1 ≠ 0, a + 2 = ± 1
A ≠ - 1, a = - 1 or - 3, a = - 3
I can't understand the formula you wrote. Anyway, just bring it in

Judge the number of roots of equation 2 ^ x = x ^ 2
RT~

This is the average problem, we need to use the equation, the problem is in the supplementary explanation
After using calculator to calculate the average of 2000 numbers, Ma xiaoha accidentally mixed the calculated average with the original 2000 numbers. Interestingly, the average of 2001 numbers is exactly 2001, and the original average of 2000 numbers is ()

2001,
Let the average be X,
According to the meaning of the question, the equation is as follows
（x+x*2000）/2001=2001,
We get x = 2001

I can use arithmetic, but I have to use equations in exams,

Suppose there are x chickens (or rabbits), then there are (total number - x) rabbits (or chickens), the number of chicken legs (or rabbits) multiplied by X + the number of rabbit legs (or chickens) multiplied by x = the total number of legs

Supplementary notes to the question,
The two ships set out from the dock 654 kilometers apart at the same time. When they were eight hours old, they were 390 kilometers apart. Ship a traveled 15 kilometers per hour. How many kilometers per hour?

Let the velocity of B be X
8*(x+15)+390=654
x=18

3 / 2 of a number plus 1 / 2 is 12 / 5. What is the number? Equation method and arithmetic method

Square method
Let this number be X
3x/2 + 1/2 = 12/5
Multiply both sides by 10 to get
15x+5=24
15x=19
x= 19/15
Formula method
（12/5 - 1/2）÷ 3/2 = 19/10 ÷ 3/2 = 19/15

Please use the simplest equation or arithmetic method. If you use the equation, please use one unknown number or two. I don't understand
If the brown sugar is increased by one third, it will be as much as the white sugar. Two thirds of the white sugar is 240kg less than the brown sugar. How many kg of brown sugar is transported from this shopping mall?

Suppose brown sugar x kg, white sugar (1 + 1 / 3) x kg
(1+1/3)x*2/3=x-240
8/9x=x-240
1/9x=240
x=2160

What are the similarities and differences between using arithmetic method and column equation to solve practical problems?

(1) The difference is: first, the formula used in arithmetic is known numbers, and the unknowns in the equation can participate in the formula. Second, because of the above reasons, the formula of the equation can be directly translated according to the meaning of the title

Elementary school application problem, can't use equation solution, must use arithmetic method!
When a ship sails between two wharves, it takes 4 hours to sail along the water and 5 hours to sail against the water. The known speed of water is 2 kilometers per hour. How many kilometers per hour does the ship travel in still water?

2 × 4 = 8 km
2 × 5 = 10 km
10 + 8 = 18 km
(5-4) × 18 = 18 km
A: the ship travels 18 kilometers per hour in still water

Requires a series of equations, one variable equation The absolute value + B = 0 of the equation (a + 1) x ^ A + 2 of X is a linear equation of one variable. We can find the value of 2A ^ 2-A / 3-A ^ 2A / 2-A ^ 2 + 5A / 6

Judge the number of roots of equation 2 ^ x = x ^ 2 RT~