(x - 40) + (x - 40) + (x - 30) = x
х - 40 + х - 40 + х - 30 = х
2х = 110
х = 110 / 2 = 55
Ответ: х = 55
8х+5=2х-1
8х-2х=-1-5
6х=-6
х=-6/6
х=-1