[tex]\qquad\qquad\huge\underline{{\sf Answer}}[/tex]
Let's solve ~
First we have to calculate g (-5) :
[tex]\qquad \tt \dashrightarrow \:x - 8[/tex]
[tex]\qquad \tt \dashrightarrow \: - 5 - 8[/tex]
[tex]\qquad \tt \dashrightarrow \: - 13[/tex]
Now, let's find f (g (-5)) :
[tex]\qquad \tt \dashrightarrow \: {x}^{2} + 6x[/tex]
[tex]\qquad \tt \dashrightarrow \:( - 13) {}^{2} + (6 \times - 13)[/tex]
[tex]\qquad \tt \dashrightarrow \:169 + ( - 78)[/tex]
[tex]\qquad \tt \dashrightarrow \:169 - 78[/tex]
[tex]\qquad \tt \dashrightarrow \:91[/tex]
