since $68 is your total, let’s use the example z=y+x

z is our total, and we know that he made a total of $68, therefore z is the number 68.

We also know that James made a total of $48 washing cars, which gives us the answer 48 as y. So in order to find x, we would need to subtract 68 and 48, which is called using the communtative property. Thsi answer would give us the remaining amount of money we do not yet know.

So 68-48= 20. therefore James made $20 at the art contest.