-12-2=-12+(-2)=-14
-7-10=-7+(-10)=-17
-3-4--3+(-4)=-7
-5-9=-5+(-9)=-14
-9-1=-9+(-1)=-10
-1-14=-1+(-14)=-15
1. 1) 2х=18-х
3х=18
х=6
2. 1) 3(х-2)=х+2
3х-6=х+2
3х-х=2+6
2х=8
х=4
3. 1) 4(5х+2)=10(2х-3)+15
20х+8=20х-30+15
20х-20х=-30+15-8
х=-23
2) 2(7х-7)=7(2х-3)+7
14х-14=14х-21+7
14х-14х=-21+7+14
х=0