3/5 + 13/45 =(3 × 9 + 13 × 1)/45 = 27/45 + 13/45 = 40/45 = 8/9
9/10 + 15/14 =(9 × 7 + 15 × 5)/70 = 63/70 + 75/70 = 138/70 = 69/35 = 1 34/35
9/16 + 11/24 = (9 × 3 + 11 × 2)/48 = 27/48 + 22/48 = 49/48 = 1 1/48
7/48 + 77/96 = (7 × 2 + 77 × 1)/96 = 14/96 + 77/96 = 91/96