Math question help.

Question

The Malcom family is renovating their kitchen and they received an estimate from their plumber of $28 per hour and $250 for parts. The total she estimated for the job is $680, so how many hours does she expect the job to take? 

Answer 1

680-250= 430= 28h

h= 430/28= 15 5/14 hours

= about 15 hours, 21 1/2 minutes