1. Вставим пропущенное.
37 + 12 = (37 + 3) + 9 = 49
54 + 35 = (50 + 4) + 35 = 89
41 + 28 = (40 + 1) + 28 = 69
Ответ: 37 + 12 = (37 + 3) + 9 = 49; 54 + 35 = (50 + 4) + 35 = 89; 41 + 28 = (40 + 1) + 28 = 69