Sam's plumbing service charges a $50 diagnostic fee and then $20 per hour. How much money does he ea

Sam's plumbing service charges a $50 diagnostic fee and then $20 per hour. How much money does he earn, m, when he shows up to your house to do a job that takes h hours

Set up the cost equation:
m = Hourly Rate * h + service charge

Plugging in our numbers, we get:
m = 20h + 50