Well, Chandler earns a base pay of 2200/month, so subtract that from his pay for the given month. 2400-2200=200. Then that answer is the solution to his sales multiplied by his commission percentage, C=S*4%. since we want sales, and have commission, a little algebra gives S=C/4%. In other words, Sales = 200/.04=5000, for the month in question.
