1. The problem statement, all variables and given/known data 2. Relevant equations D = rt 3. The attempt at a solution This is my attempt let d= length of the circuit 60/a mph --- speed for walking 60/b mph ----speed for riding 60/c mph ---- speed for driving d=(60/a)t1+(60/b)t2+(60/c)t3 From here I cannot continue. Kindly help me. Thanks!