(X+ 10)7/ 12=X+2

X=46/5

4. solution: suppose that the price of this commodity is x yuan per piece.

(0.9X-250)/250= 15.2%

X=320

5. Solution: Let each box have X products.

(8X+4)/5- 1 =( 1 1X+7)/7

X= 12

6. Solution: Let the speed of the two cars be equal after X hours.

30+20X=90- 10X

X=2

Speed: 30+20 * 2 = 70

Sorry, I can't do the seventh question either.

8. Solution: (1) Let the speed of the first five hours be x km/h, then the speed of the middle five hours be (x+20) km/h, and the speed of the last five hours be (x+ 10) km/h, then 5x+5 (x+20)+5.

(2)74 times 5+94 times 3 = 652km.

9.( 1)

Solution: Diophantine lived for X years.

x = 1÷6x+ 1÷ 12x+ 1÷7x+5+ 1÷2x+4

x=25÷28x+9

x-25÷28=9

3÷28x=9

x=9÷3*28

x=84

A: It can be seen that Diophantu lived to be 84 years old.

(2)

12×7=84 answer: the answer is the product of the largest coprime factors in 12, "6" and "7"-"12× 7 = 84".

Diophantine's father's age: 84× (1÷ 6+1÷12+1÷ 7)+5 = 38 (years old) A: Diophantine's father's age is 38.

3. Diefantu's son died at the age of 84-4=80 (years old) A: Diefantu's son died at the age of 80.

Hope to adopt, thank you for your cooperation.