What you want to do is make a common denominator (the bottom number)
So does 3 go into 12? Yes it does (3 x 4)
So since you times the 3 by 4 you have to times the 2 by 4 aswell (so that it stays the same number just on a diffrent scale) the 2/3 becomes 8/12 (which is also 2 thirds) so you do 7/12 + 8/12 (7 twelths plus 8 twelths) which becomes 15/12 (15 - 12 = 3
So it comes 1 3/12 or 1 1/4)
