Easy all you have to do is do 3 + 9 equals 20 which we all know that because we're in high school haha anyways back to what you do 3 + 9 which equals 12 we do we have to flip it around so if you sent it around it will be 12 equals 9 + 3 no I just read it so it would be 12 plus 9 which equals 3 which we know that so you have to flip the device which is going to eat with 3 or 12 - 9 which is going to eat you 3 that's what I'm going to put with that
you get 2 coordinates x one, y one, x two, and y two and then do rise over run which is y two - y one over x two - x one say x one is 4 and y one is 7 and x two is 8 and y two is 13 you say 13-7=6 and 8-4=4 so it is 6/4 hope that makes sense
