7 14/15 + 2 1/15 = (7 + 2) + (14/15 + 1/15) = 9 + 15/15 = 9 + 1 = 10
9 24/27 + 12 13/27 = (9 + 12) + (24/27 + 13/27) = 21 + 37/27 = 21 + 27/27 + 10/27 = 21 + 1 + 10/27 = 22 10/27
16 3/13 - 6 8/13 = (16 - 6) + (3/13 - 8/13) = 10 - 5/13 = 9 + 1 - 5/13 = 9 + 13/13 - 5/13 = 9 8/13
13 4/9 - 2 8/9 = (13 - 2) + (4/9 - 8/9) = 11 - 4/9 = 10 + 1 - 4/9 = 10 + 9/9 - 4/9 = 10 5/9