the time for the bike = x
the time for the runner = x+2 ( started 2 hours before bike)
runners speed = 6, bike speed = 16
so you have 6(x+2) = 16x
distribute the left side:
6x +12 = 16x
subtract 6x from each side:
12 = 10x
divide both sides by 10
x = 12/10
x = 1.2 hours
1 hour = 60 minutes
1.2 x 60 = 72 minutes