5 4/15 + 8 1/3 = 5 4/15 + 8 5/15 = 13 9/15 = 13 3/5
-6 2/7 - 3 3/14 = -6 4/14 - 3 3/14 = - 9 7/14 = - 9 1/2
4 10/11 - (-1 1/22) = 4 20/22 + 1 1/22 = 5 21/22
4 11/12 - 7 13/18 = 4 33/36 - 7 26/36 = -(7 26/36 - 4 33/36)= - (6 62/36 - 4 33/36) = - 2 29/36