A plumber charges $75 for the first 30 minutes of each house call plus $2 for each additional minute that she works. The plumber charges Adam $113 for her time. For what amount of time, in minutes, did the plumber work?
We can construct a formula for the plumber's fee.
The red 75 denotes the $75 that is charged for the first half hour.
Cost is $113 so
Can subtract 75 from both sides of the equation without changing anything about it:
Divide both sides by 2:
She worked 19 minutes over the first 30, so worked