It rained 3 + 4 = 7 inches. So he collected 7 * 15 = 105 gallons. So he makes 105 * 1.2 = $126 from selling the water.
This justifies what answer for what question? Q & A:
James has a rainwater collection barrel. For each inch of rain he collects 15 gallons. On Monday it rained 4 inches and on Tuesday it rained 3 inches. He can sell water for $1.2 per gallon. How much money did he make from selling all the water?
126