In order to find the value of (f+g)(-1), first let's find the composite function (f+g)(x):
[tex]\begin{gathered} (f+g)(x)=f(x)+g(x)\\ \\ =3x+3+6x+6\\ \\ =9x+9 \end{gathered}[/tex]
Now, let's use x = -1 and calculate its value:
[tex](f+g)(-1)=9\cdot(-1)+9=-9+9=0[/tex]
Therefore the value of (f+g)(-1) is equal to 0.
