31 13/16+13 17/28=

(43 7/9+45 3/8) - 62 3/8=

31 13/16 + 13 17/28 = 509/16 + 381/28 = (509 * 7 + 381 * 4) / 112 = (3563 + 1524) / 112 = 5087/112 = 45 47/112

(43 7/9+45 3/8) - 62 3/8=26 7/9

1) 43 7/9 + 45 3/8 = 394/9 + 363/8 = (394 * 8 + 363 * 9) / 72 = (3152 + 3267) / 72 = 6419/72 = 89 11/72

2) 89 11/72 - 62 3/8 = 6419/72 - 499/8 = (6419 * 1 - 499 * 9) / 72 = (6419 - 4491) / 72 = 1928/72 = 241/9 = 26 7/9