On Saturday, you spend $33, give $15 to a friend, and receive $20 for mowing your neighbor’s lawn. You have $21 left. Use two methods to find how much money you started with that day.
I don't have two methods....but.....here's one.......call M the original money that you started with....so we have.....
M - 33 - 15 - 20 = 21 simplify
M - 68 = 21 add 21 to both sides
M = $89