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