The first problem can be solved by an unknown number or formula. The formula is as follows:

3.8-0.2 = 3.6m.

3.6×190 = 684m

684÷3.6= 180 (set)

A: Originally, only 180 sets could be made.

The second question:

The speed must have a distance to find the time, and the formula is as follows:

Solution: let a and b be x meters.

(60+ 190)× time =X-65

250× time =X-65

X=250+65÷ Time

X=3 15÷ time

X=？

Solution: suppose two people meet at a distance of 65 meters from the midpoint after x minutes.

(60+ 190)× X = total distance -65.

X=？

8.08 tons = 80 kg

The key is the process of solving the problem, one ton = 1000 kg.

Can it be solved?