15) 8х - 10 = 6х + 20
8х - 6х = 20 + 10
2х = 30
х = 30 ÷ 2
х = 15;
16) 17х - 1 = 15 + 16х
17х - 16х = 1 + 15
1х = 16
х = 16;
17) 19 + 3х = 5х - 15
5х - 3х = 19 + 15
2х = 34
х = 34 ÷ 2
х = 17;
18) 6 + 2х = 4х - 30
4х - 2х = 30 + 6
2х = 36
х = 36 ÷ 2
х = 18;
19) 5х + 3 = 4х + 22
5х - 4х = 22 - 3
1х = 19
х = 19;
20) 2 + 2х = х + 24
2х - х = 24 - 2
1х = 22
х = 22;
21) 5 + 7х = 26 + 6х
7х - 6х = 26 - 5
1х = 21
х = 21.