Two cars start at a given point and travel in the same direc

Two cars start at a given point and travel in the same direction at average speeds of 48 miles per hour and 56 miles per hour. How much time must elapse before the two cars are 12 miles apart?

Solution

56x=48x+12
56x-48x=12
8x=12
x=12/8
x=1.5 hours they will be 12 miles apart.
Proof:
56*1.5=48*1.5+12
84=72+12
84=84