Question 998808
 *[illustration greg]

Joy rides7 km = 7000 m at x m/s

time up = 7000/x

time down = 10000/2x

Time up + time down for joy = time by greg to reach the starting

7000/x + 10000/2x = 3000

multiply by 2x

14000 +10000 = 2x*3000

24000 = 6000x

x = 4 m/s up the hill

downhill 4*2 = 8 m/s