(3 - 2х) + (4 - 3х) + (5 - 5х) =12 + 7х

(3-2х)+(4-3х)+(5-5х)=12+7х3-2х+4-3х+5-5х=12+7х-2х-3х-5х-7х=12-3-4-5-17х=0х=0:(-17)х=0=================