14/15+11/12-1 7/10=?Помогите, пожалуйста...

14/15 + 11/12 - 1 7/10 = 3/20 1) 14/15 + 11/12 = 56/60 + 55/60 = 111/60 = 1 51/60 2) 1 51/60 - 1 7/10 = 1 51/60 - 1 42/60 = 9/60 = 3/20 Пояснения: 14/15 = (14*4)/(15*4) = 56/60 - доп.множ. 4 11/12 = (11*5)/(12*5) = 55/60 - доп.множ. 5 7/10 = (7*6)/(10*6) = 42/60 - доп.множ. 6 9/60 = (9:3)/(60:3) = 3/20 - сократили на 3