SPEEDS TIMES DISTANCE BIKE r +10 12/(r+10) 12 WALK r 8/r 8 TOTAL 5
Let r is the rate biking, in miles per hour. Then the rate hiking is (r-10) mph. Your time equation is+ = 5 hours. (*) The answer is obvious and you can get it mentally: the rate biking is 12 mph; the rate hiking is 2 mph. If you want to get a formal algebra solution, you can multiply eq(*) by r*(r-10) (both side) and then solve the obtained quadratic equation.