5 1/10 + 8 3/8 = 51/10 + 67/8 = (51 × 4 + 67 × 5)/40 = 204/40 + 335/40 = 539/40 = 13 19/40
9 3/20 + 7 4/15 = 183/20 + 109/15 = (183 × 3 + 109 × 4)/60 = 549/60 + 436/60 = 985/60 = 197/12 = 16 5/12
6 11/12 + 3 15/16 = 83/12 + 63/16 = (83 × 4 + 63 × 3)/48 = 332/48+189/48 = 521/48 = 10 41/48