24÷36=2/3

It's actually two-thirds of the plan.

2.

Coal tonnage per vehicle = 18÷6÷2= 1.5 tons.

Coal tonnage per vehicle =60÷5÷3=4 tons.

therefore

1.5÷4=3/8

that is

The tonnage of coal transported by each big car is 3/8 of that transported by each small car.