Algebra need help

Question

A production line produces 3/4 of a mile of yarn every 1/4 of an hour. What is the unit rate of miles of yarn per hour

Answer 1

3/4 of a mile of yarn every 1/4 of an hour

3/4 mile per 1/4 hour

(3/4) mile / (1/4) hour

(3/4)/(1/4) miles per hour

(3/4)(4/1) miles per hour // invert and multiply

3 miles of yarn per hour