Question

A car traveled at an average rate of 51 miles per hour on one highway. It then traveled at an average rate of 71 miles per hour on a second highway. If the car traveled a total of 508 miles in 8 hours, how many miles were driven on the first highway?

Answer 1

d1 = 51(t)

d2 = 71(8 - t)

d1 + d2 = 508

and now you just have to solve for t.