2. Suppose it takes X minutes to walk 70 meters per minute, 70*x=90*(x-8), and solve this equation, x=36, so the current time is x-8=36-8=28 minutes.

Each rabbit has four feet, and the chicken has two feet. X rabbit and chicken are (125-x), 4x-2( 125-x)=68.

4x-(250-2x)=68

4x-250+2x=68

6x=3 18

x=53， 125-53=72

4. Are there any mistakes? The decimal point moves to the right to get bigger and then to the left to get smaller. Let the original number be x and the decimal point be shifted one place to the left, and the number obtained is 0. 1x, which is reduced by 10 times, and the subtraction result is 0.9x=43.65.

x=48.5

5. 100t seawater can be used to make salt, 120kg, 100÷ 120 (how many tons of seawater is needed to make one kilogram of sea salt), 120÷ 100 (per

6. The sum of the ages of Xiao Pang and his father this year is 52. Xiao Pang is 28 years younger than his father. How much are Xiao Pang and his father this year?

Solution: Let Dad be X years old and Xiao Pang be (52-x) years old (hint: Xiao Pang is 28 years younger than Dad, that is, Dad is 28 years older than Xiao Pang).

Equation: x-(52-x)=28.

Solution: Let Xiao Pang be x years old and Dad be (28+x) years old.

Equation: (28+x)+x-=52.

Solving application problems with column equations;

1 A square is reduced by 5cm and 8cm to get a rectangle. Its area is 259cm2 smaller than that of a square. What is the area of a square?

Let the side length of a square be x meters, (x-8)*(x-5)+259=x*x (This topic is a bit difficult, which is easy for junior high school students to understand and can be solved by courageous primary school students. )

2. Xiao Pang and Mix compete on the 1000-meter-long circular track. Mix speed is 140m/min, and Xiaopang speed is 180m/min.

(1) If they start from the same place and walk past each other at the same time, how many minutes later? (Is this your first meeting? )

Let's meet in x minutes, (140+180) * x =1000.

(2) If they are in the same place and heading in the same direction, how many minutes will it take them to meet?

The runner ran an extra lap. I'll see you in x minutes.180 * x =1000+140 * x.

3. Two trains, A and B, travel in opposite directions from A and B at the same time. A walks 48 kilometers per hour and B walks 52 kilometers per hour. The two cars meet at the midpoint of 12 kilometers. The distance between a and b (hint: it is best to draw and analyze. )

Suppose the distance is not xkm, half is 0.5xkm, and the travel time of two cars is the same (/symbol is division symbol).

(0.5x+ 12)/52 =(0.5x- 12)/48

4. The school bought 720 books for the senior, middle and junior grades. After sorting, the junior grade gave the senior grade 15 books and the middle grade gave the junior grade 5 books. At this time, the number of books in senior grades is three times that of middle grades, and the number of books in middle grades is twice that of junior grades. How many books were distributed in the first three grades?

Suppose there are x books in the lower grades, 2x books in the middle grades and 6x books in the upper grades.

x+2x+6x=720

So there are (x+ 15-5) books in the lower grades, (2x+5) books in the middle grades and (6x- 15) books in the upper grades, which can be calculated.

The fruit shop sent a batch of apples, which were sold in two grades: 1 and 2. 1 Grade unit price per kilogram of 8 yuan and Grade II unit price per kilogram of 6 yuan. If the price is reduced by 1.5 yuan per kilogram, how many kilograms are there in each of the two grades 1 and 2?

If you use two unknowns, it's very simple, I'm afraid you won't,