Akash takes the race first in unity time. Therefore
100 = v_akash * 1
At this unity time,  Andrew lags by 20 meters. Therefore
80 = v_andrew *1
Andrew finishes the race in time t_2. Therefore using the last relation
100 = 80 t_2
or t_2 = 10/8
At this time t_2, we know that andrew beats allen by twenty meters. So Allen is at 80 meters at time t_2
80 = v_allen * 10/8
or v_allen = 64.
So at t_1, Allen is at 64m. So Akash beats Allen by 100 – 64 = 36 m.

36 meters