Solve:

20-9x=11

4 (2x+1) = 8

5 (2x+5) = - 15

3 (8x+1) = - 21

20-9x=11

-9x=11-20

-9x = - 9

x = - 9 / (-9)

x=1

4 (2x+1) = 8

2x+1=8/4

2x+1=2

2x=2-1

2x=1

x=1/2

x=0.5

5 (2x+5) = - 15

2x+5 = - 15/5

2x+5 = - 3

2x = - 3-5

2x = - 8

x = - 8/2

x=-4

3 (8x+1) = - 21

8x+1 = - 21/3

8x+1 = - 7

8x = - 7-1

8x = - 8

x = - 8/8

x = - 1