-4x-21 = -7x-3
5-4x=7-5x
-3x-10=-12-5x
13-4x=1-8x
7x+10=5x+12
9x+13= 5x+4

Ответ:

1).-4х+7х=-3+21

3х=18

х=6

2)-4х+5х=7-5

х=2

3)-3х+12х=-12+10

9х=-2

х=-2/9

4)-4х+8х=1-13

4х=-12

х=-3

5)7х-5х=12-10

2х=2

х=1

6)9х-5х=4-13

4х=-7

х=-7/4