Higgins Rental charges $ 18 an hour to rent a power tool in addition to a $9 flat service fee. If Joseph rents a power tool and is charged $ 423, how many hours did he rent the tool?

Question

Hint: Convert the above scenario into an equation of the form A x + B = C.

I need help to get to the right direction of this problem to get the right answer

Answer 1

423 - 9 = 414

414/18 = 23

Answer 2

But the formula doesnt work because its gotta b in ax+b=c equation