"One rotation" would be the circumference of the wheel, which is
C = 2*pi*r, or (here) C = 2*pi*(8 inches) = 16*pi inches.
1 ft
Convert this to feet: 16*pi inches times ---------------
12 inches
Here "inches" cancels out and you are left with (4/3)pi ft.
So, one rotation of the wheel moves you and your bike forward (4/3)pi ft.
Divide this into 700 feet:
700 ft 2100
------------- = --------- rotations = 525 rotations (answer)
(4/3) pi ft 4