Xavier spent $84 on supplies (so this is an expense we will make only once), and then he will spend one more dollar for each canvas. So, his total expense for
paintings will be
Similarly, he will get 8 dollars for each painting, so he will earn
dollars if he will sell
paintings.
In order to break even, earnings and costs must be equal:
Subtract p from both sides:
Divide both sides by 7:
So, he has to sell at least 12 paintings to break even.