Jennifer uses the formula P = 0.5e - 5 to determine the profit (P) she makes from selling any number of erasers (e). Last week Jennifer had a profit of $63. How many erasers did Jennifer sell?

To find this answer we must plug in the values given and then rearrange the equation to solve for e (number of erasers). First we can rearrange the equation for e to get the following expression: (P + 5) /.5 = e. Now we just plug in the $63 profit for P and solve for e. Doing this we get: (63 + 5) /.5 = 68/.5 = 136. Jennifer sold 136 erasers.