in a bike competition with 21 laps was observed that 13% quit before 5 laps, 17% quit later than 5 laps but less than 15, and the others 210 finished the competition the number of bikers that quit before the 5 lap were:
a) 27
b) 39
c) 43
d) 56
13%+17% = 30% who quit
So, 210 were the remaining 70%
210/.7 = 300
13% of 300 = 39