20(30-x)= 2.5

x=22

2. Set the correspondent to catch up with the student team of the class (1) in x minutes.

75(20+x)=225x

x = 1

3、72*4/(4-0.4)=80 km/h。

4. Suppose that the car passes the bus 13.6km after driving for x hours.

108 X- 13.6 = 92 *(X+0.2)

108 x- 13.6 = 92X+ 18.4

108 x-92X = 13.6+ 18.4

16X=32

X=2

5. Set X to catch up.

Then 170x-70x=70*5.

Solution x=3.5 minutes.

6. Meeting time =2300×2÷( 150+80)=20 minutes.

Sister, please: 20×80= 1600 meters.

7. Suppose my mother walks home from work for x minutes today, which usually takes X+4 minutes.

70X=60(X+4)

70X-60X=240

10X=240

X=24

8. Set up the car and drive for x hours before catching the bus.

1 10X=88*(X+0.3)

1 10X=88X+26.4

22X=26.4

X= 1.2

It took 1.2 hours to catch the bus.

Hope to adopt, I'm exhausted.