You can put this solution on YOUR website! $12.00 times 20 = $144 . You multiply How much she earns an hour witch is 12 dollars by how many hours she works witch is 20 and get 144 dollars. $15 times 15= 225. You multiply much much she earns per unit sold which is 15 dollars times how much unit she sold which is 15 and you get 225 dollars. Now add $144 and $225 and you get $369.