Ответ:

a)4/15 : х = 2/5

Х= 4/15 : 2/5

Х= 4/15 * 5/2

Х= 2/3

б)2/15у + 3/4 = 5/6

2/15у = 5/6 - 3/4

2/15у = 10/12 - 9/12

2/15у = 1/12

У= 1/12 : 2/15

У = 1/12 * 15/2

У= 15/24

в)5/8m - 7/12m+ 5/6m = 1/4

15/24m - 14/24m + 20/24m = 1/4

21/24m = 1/4

m = 1/4: 21/24

m = 1/4 * 24/21

m = 6/21