How many hours did the job take?

Question

Mark fixes furnaces. He charges $25 per visit, plus $12 per hour. If he billed a customer $45 for one visit, write an equation that could be used to find the number of hours Mark billed for?

Answer 1

In general, when there's a starting amount and then an amount per something, it's a linear equation: y = mx + b. b is the starting amount, and m is the amount per something - the something is x.

y is the charge in this case, and x is the number of hours.

y = 12x + 25

The question mentions the total bill is 45: y=45.

45 = 12x + 25 That's the equation you can use to solve for x, the number of hours worked and billed.

45 - 25 = 12x

20/12 = x = 5/3.