По действиям в) (2/5 - 2/7) : 2/7 * 2/5 г) (5/6 - 3/10) : (3/10 + 2/15)

в) (2/5 - 2/7) : 2/7 * 2/5 = 4/25,

1) 2/5 - 2/7 = 14/35 - 10/35 = 4/35,
2) 4/35 : 2/7 = 4/35 * 7/2 = 2/5,
3) 2/5 * 2/5 = 4/25,

г) (5/6 - 3/10) : (3/10 + 2/15) = 1 3/13,

1) 5/6 - 3/10 = 25/30 - 9/30 = 16/60 = 8/15,
2) 3/10 + 2/15 = 9/30 + 4/30 = 13/30,
3) 8/15 : 13/30 = 8/15 * 30/13 = 16/13 = 1 3/13

В)
(2/5-2/7):2/7*2/5=(-0,2):27/10*5/2=(-1/5:27/10*5/2=-10/27*1/2=-5/27
г)
(5/6-3/10):(3/10+2/15)=8/15:13/30=8/15*13/30=8/15*30/13=8*2/13=16/36