7/ 12x*(x+ 10)=x+2

x=9.2

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 1x+ 1)/7+ 1

(8x+4)* 7 =( 1 1x+ 1)* 5+35

56x+28 = 55x+5+35

56x-55x=40-28

x = 12

6. solution: suppose x hours later.

30+20x=90- 10x

20x+ 10x=90-30

30x=60

x=2

Speed:

30+20*2

=30+40

=70 km/h

7.( 1) Let the per capita quota of this month be X pieces.

(4x+20)/4=(6x-20)/5

x=45

(2) Let the per capita quota of this month be X pieces.

(4x+20)/4=(6x-20)/5+2

x=35

(3) Let the per capita quota of this month be X pieces.

(4x+20)/4=(6x-20)/5-2

x=55

8.( 1) Let the speed of the first section be x.

5x+5 *(x+20)+5 *(x+20- 10)= 1262

x=74

The speed of the second section is 74+20=94 kilometers per hour.

The speed of the third section is 74+20- 10=84 kilometers per hour.

(2)8 hours' journey =74*5+94*(8-5)=652 kilometers.

In the map scale problem, I was not set to I.

652I represents the distance from Beijing on the map.

9.( 1).84 (2).38 (3).80