a moving company charges $45 on arrival and $25 and hour. Their final bill was $470. How many hours did they work.

Let's x to be hours that company worked.

Then, $ 25x should be billed for x hours.

Altogether is going to be charged $ 45 + 25x.

So,

45 + 25x = 470

25x = 425

x = 17 (hours)

Answer: a company worked 17 hours.