Freight yard unloading slogan

We assume that each vehicle carries 1 cargo per hour.

The discharge capacity of the ship per hour is: (9×12-8×16) ÷ (16-12) = 5 (copies).

The original inventory on the freight yard is: 108-5× 12=48 (copies).

After three cars 10 hour, there are goods on the yard: 48+(5-3)× 10 = 68 (copies),

Clear the scene in 4 hours, and the quantity of * * * transported goods is 68+5×4=88 (copies).

The number of vehicles required is: 88÷4=22 (vehicles),

Add 22-3= 19 (vehicle).

A: The number of cars added later was 19.