Respuesta :

3/8 (14.5) = 43.5/8 = 5.44 (this is rounded)..so he has already biked 5.44 miles

14.5 - 5.44 = 9.06 miles <== this is how many miles he has left to bike

or this way...
if he already biked 3/8, then he has 5/8 left to bike
5/8 (14.5) = 9.06 miles