You first take 538 and put it on the top. The you put 247 below it. You do 8 minus 7 and get 1. 1 is in the ones digit. You then do 3-4, which you cant so you have to borrow. Borrow from the 5, 5 turns into 4. 3 turns into 13. 13-4 is 9. 9 is in the tens place. 4-2 is 2. So the answer is 291