Question 604151
Truck's speed = T
Car's speed = C


T = C - 5


165/T = 180/C
165C = 180T
(divide all by 15)
11C = 12T
11C = 12*(C - 5)
11C = 12C - 60
60 = 12C - 11C
60 = C


So, the average speed of the car is 60 mph, and the truck is 60 - 5 = 55 mph