2. Let the weight of coal be a, the original coal+water is m, and now coal+water is a countable equation with the same weight of coal.

A = (1-14.5%) m = (1-10%) m, so m = 85.5%/90% m.

3. Let the sales volume without price be A, the sales volume with price be B, and the price of each commodity be X..

AX=BX*( 1- 10%), so B= 10/9A.

4. Suppose their ages are different, and X, A and B are Ba-2x = 4b-x = 4b+2x = 61a+x = 61.

So A=42 B=23

5, that is, find the least common multiple of 4 5 6. /kloc-it will leave at the same time in 0/20 minutes, which is 9 o'clock.

8. Let the minimum age be x, so x * (x+1) * (x+2) * (x+3) = 5040, so X= you calculate it yourself.

7, the aspect ratio is 3: 2, so the area of a square with an area of 6 should be a positive integer multiple of 6. Let the side length of a square be X X=3a+2b X squared =6c. Find the minimum value of c, and it's OK.

The area of 6,4: 3 is 36 square decimeters, with 12.