Answer:
[tex]{ \tt{f(x) = 6 - 2x}}[/tex]
[tex]{ \tt{6 - 2x = - 8}} \\ \\ { \tt{2x = 6 + 8}} \\ \\ { \tt{2x = 14}} \\ \\ { \tt{x = \frac{14}{2} }} \\ \\ { \underline{ \tt{ \: \: x = 7 \: \: }}}[/tex]