Question

Luis rides his bicycle 3:4 of a mike in 5 minutes,or 1:12 hour,along the bike trail.Assuming he rides at a constant rate,what is his speed,in miles per hour?

Answer 1

I assume that you mean:
"Luis rides his bicycle 3/4 of a mile in 5 minutes"

Since 5 minutes is 1/12 of an hour, like you stated

rate = distance/time
= (3/4) / (1/12) mph
= 9 mph

Answer 2

9minutes