Ryan left the science museum and drove south. gab left 3 hours later driving 42km/h faster in effort to catch up to him. after 2 hours gab finally caught up. Find Ryan's average speed.

Distance = speed x time (D=vt) Let R=Ryan's speed. Ryan drove 5 hrs. Gabe drives only 2 hours to get just as far. So their distances are equal in the end. So then using D=vt for each distance and setting them equal:

5R=2 (R+42)

5R=2R+84

3R=84

R=28km/hr