Пошаговое объяснение:
25/28-2/21 = 75/84 - 8/84 = 67/84
41/54-35/72 = 164/216 - 105/216 = 59/216
20/21-3/14 =40/42 - 9/42 = 31/42
40/143+39/110 = 400/1430 + 507/1430 = 907/1430
43/140+41/150 = 645/2100 + 574/2100 = 1219/2100
73/80-37/100 = 365/400 - 148/400 = 217/400
