Xavier drove from his house to the country in 3 hours. driving at a speed of 12 mph less than on the trip out, he spent 4 hours on the return trip. what was his average rate on the return trip?

  36 mph

Step-by-step explanation:

Let s represent the return trip speed. Then s+12 will be the speed on the trip out. The distance is presumed the same on both trips. We can use ...

  speed · time = distance

  (3)(s +12) = 4(s)

  36 = s . . . . . . . . . . . subtract 3s and simplify

The return trip speed was 36 miles per hour.