We have the following functions:
[tex]\begin{gathered} f(x)=x^2-3x-9 \\ g(x)=2x \end{gathered}[/tex]We need to find g(8) + f(-3). The expression g(8) is equivalent to replace 8 in the place of x, that is,
[tex]\begin{gathered} g(8)=2(8) \\ \text{then, } \\ g(8)=16 \end{gathered}[/tex]Similarly, f(-3) is given by
[tex]f(-3)=(-3)^2-3(-3)-9[/tex]which gives
[tex]\begin{gathered} f(-3)=9+9-9 \\ f(-3)=9 \end{gathered}[/tex]Therefore, g(8)+f(-3) is given by
[tex]g\mleft(8\mright)+f\mleft(-3\mright)=16+9[/tex]so the answer is 25
