(6 7/12 - 5 11/15) * (13/17 - 10/17) = 3/20
1) 6 7/12 - 5 11/15 = 6 35/60 - 5 44/60 = 5 95/60 - 5 44/60 = 51/60 = 17/20
2) 13/17 - 10/17 = 3/17
3) 17/20 * 3/17 = 3/20
Пояснения:
7/12 = (7*5)/(12*5) = 35/60 - доп.множ. 5
11/15 = (11*4)/(15*4) = 44/60 - доп.множ. 4
6 35/60 = 5 + 60/60 + 35/60 = 5 95/60
51/60 = (51:3)/(60:3) = 17/20 - сократили на 3