Question

Carlos walks 4 miles every night for exercise. Its takes him exactly 64 minutes to finish his walk.

Answer 1

The answer would be 64x=4

Answer 2

Ok, so if he walks 4 miles per 64 minutes, or 4 miles/64 min which will reduce to 1 mile/ 16 min,  then the numbers of miles he walks in a given number of minutes would be

1/16 * number of minutes

The question states we represent miles with y and number of minutes with x, so...

y = 1/16x

So let's check it...

How many miles (y) in 64 minutes (x)

y = 1/16x
y = 1/16 * 64
y = 64/16 = 4 miles 

Yep! It checks!