3) x/3 - x/15 = (приводим к общему знаменателю) 5x/15 - x/15 = 4x/15;
x/5 + 2/3 = 3x/15 -10/15 = (3x - 10)/15;
4x/15 = (3x - 10)/15;
(cокращаем на 15) 4х = 3х - 10;
х = -10.
4) х/8 - х/6 = 3х/24 - 4х/24 = -х/24;
х/4 - 7/8 = 2х/8 - 7/8 = (2х - 7)/8;
-х/24 = (2х -7)/8;
-8х = 48х - 168;
-56х = 168;
х = -3.