For this case, the first thing we must do is define variables.
We have then:
x: number of classes:
y: total cost
For Devin we have the following equation:

For Jared we have:

Then, by the time the cost of both is the same, we have:

From here, we clear the value of x.
We have then:




Answer:
it takes 10 classes for Devin's total cost to equal Jared's total cost