Answer :

We have to mutiply factor -2/3 times every agument from the parenthesis.
[tex]8-2b=- \frac{2*12b}{3}- \frac{2*6}{3} \\ 8-2b= -8b-4 \\ [/tex]     /+8b
8+6b=-4         /-8
6b=-12         /:6
b=-2 - its the answer
[tex]8-2b=-\frac { 2 }{ 3 } \left( 12b+6 \right) \\ \\ 8-2b=-\frac { 2 }{ 3 } \cdot 12b-\frac { 2 }{ 3 } \cdot 6\\ \\ 8-2b=-\frac { 24 }{ 3 } b-\frac { 12 }{ 3 } \\ \\ 8-2b=-8b-4\\ \\ -2b+8b=-4-8\\ \\ 6b=-12\\ \\ b=\frac { \left( -12 \right) }{ 6 } \\ \\ \therefore \quad b=-2[/tex]