We are asked to find the sum of the following expressions
[tex](-6x+6)\: \: and\: \: (-3x-7)[/tex]First of all, expand the parenthesis
[tex]\begin{gathered} (-6x+6)+\: (-3x-7) \\ -6x+6-3x-7 \end{gathered}[/tex]Now, collect the like terms together and add/subtract
[tex]\begin{gathered} -6x+6-3x-7 \\ (-6x-3x)+(6-7) \\ (-9x)+(-1)_{} \\ -9x-1 \end{gathered}[/tex]Therefore, the sum of the given expressions in the simplest form is
[tex]-9x-1[/tex]