(Junior high schools generally don't use arithmetic to learn setting elements ... and setting elements to solve problems is relatively simple) 1: Set x minutes.

300÷X-200÷X=20

(300-200)X = 20

100 \x = 20

X= 100÷20

X=5

300 ÷ 5 = 60 ÷ 200 ÷ 5 = 40 Answer ——————

2. Deconstructed and purchased X units.

1000 X-800 X = 10

( 1000-800)÷X= 10

200 \x = 10

X=200÷ 10

X=20

1000÷20=50 800÷20=40

(These two questions seem to be similar ...)

There are two ways to solve this problem. ...

1: Li Yangjia -0.5km- School -2.5km- Wang Xiaoming's home.

2. Wang Xiaoming home-3km-Liyang home-0.5km-school.

Let's count the first one ... It takes x minutes to solve Li Yang's problem on foot. It takes X+20 minutes to pick up Wang Xiaoming by bike.

3÷(X+20)=0.5÷X×3

3X= 1.5×(X+20)

3X= 1.5X+30

1.5x = 30 0.5÷ 20 = 0.025km.

X = 20 3÷ (20+20) = 3÷ 40 = 0.075km.

The second type

3.5÷(X+20)=0.5÷X×3

3.5X= 1.5×(X+20)

3.5X= 1.5X+30

2X=30 0.5÷ 15= 1/30 (km)

X =153.5 ÷ (15+20) = 3.5 ÷ 35 =110 (km)

If it is not detailed enough, please tell me why I do it every step of the way ... These four questions are all done by myself ... I hope the landlord will adopt them. ....

I want to ask my brother on the fourth floor, did you draw the third question? Did you do the checking calculation? According to your answer, 4 ÷1/4 =160.5 ÷112 = 60, please tell me 60- 16=20.