7/15 + 8/15, 1- 28/60, 1-8/80,решите примеры

7/15 + 8/15 = 15/15 =1 1 - 28/60 = 60/60 - 28/60 = 32/60 = 8/15 1 - 8/80 = 1 - 1/10 = 10/10 - 1/10 = 9/10