During summer vacation, you charge people 8$ per hour for swimming lessons and 20$ registration fee. If you make 52$ one day, how many hours did you spend teaching lessons?

You taught for 4 hours

Step-by-step explanation:

Let this number of hours be x.  Then:

Total earned = $20 + ($8/hr)x

Equate this to $52 and then solve the resulting equation for x:

20 + 8x = 52

Then 8x = 32, and x = 4.  You taught for 4 hours.

1/800 is the right answer