my question about (Solving a value mixture problem using a system of linear equations)

Question

Two mechanics worked on a car. The first mechanic charged $105

 per hour, and the second mechanic charged $110

 per hour. The mechanics worked for a combined total of 15

 hours, and together they charged a total of $1600

. How long did each mechanic work?

Answer 1

$105 per hour, $110 per hour total 15 hours total bill $1600

105x + 110y = 1600

x + y = 15

105x + 105 y = 1575

subtract to get 5 y= 25

y=5 hours = time the $110 per hour mechanic worked

x=10 hours = time the $105 per hour mechanic worked

10(105) + 5(110) = 1050 + 550 = 1600