7/10-2/5*(1/4+5/6):6,1/2

1/4 + 5/6 = 3/12 + 10/12 = 13/12
2/5 * 13/12 = 1/5 * 13/6 = 13/30
13/30 : 6,1/2 = 13/30 : 13/2 = 13/30 * 2/13= 1/15
7/10  -  1/15 = 21/30 - 2/30= 19/30

1) 1/4+5/6= 6/24+20/24=26/24=1. 2/24=1. 1/12
2) 2/5* 1. 1/12= 2/5* 13/12= 1/5* 13/6= 13/30
3)13/30:6,12=13/30:6.12/100=13/30:612/100=13/30*100/612=130/1836=65/918
4) 7/10-65/918=3213/4590-325/4590=2888/4590=1444/2295
Ответ:1444/2295