Question 581263
Distance(d) equals rate(r) times Time(t) or d=rt;  r=d/t and t=d/r

Now we know that bike A and Bike B are approaching each other at the rate of 10+5=15 mph
Time it takes bikes to collide=t=d/r=15/15=1 hour
Sooooo, the fly has 1 hour of flying time before it gets squashed and in the one hour, it travels a distance of d=rt=20*1=20 mi


Hope this helps--ptaylor