Let's solve this step-by-step.
1. Find the expression for [tex]\((g - f)(x)\)[/tex]:
[tex]\(f(x) = 3x\)[/tex]
[tex]\(g(x) = 2x + 6\)[/tex]
[tex]\[
(g - f)(x) = g(x) - f(x) = (2x + 6) - 3x = 2x + 6 - 3x = -x + 6
\][/tex]
So, [tex]\((g - f)(x) = -x + 6\)[/tex].
2. Find the expression for [tex]\((g \cdot f)(x)\)[/tex]:
[tex]\[
(g \cdot f)(x) = g(x) \cdot f(x) = (2x + 6) \cdot 3x = 6x^2 + 18x
\][/tex]
So, [tex]\((g \cdot f)(x) = 6x^2 + 18x\)[/tex].
3. Evaluate [tex]\((g + f)(3)\)[/tex]:
[tex]\[
g(x) = 2x + 6
\][/tex]
[tex]\[
f(x) = 3x
\][/tex]
[tex]\[
(g + f)(x) = g(x) + f(x) = (2x + 6) + 3x = 2x + 6 + 3x = 5x + 6
\][/tex]
To evaluate [tex]\((g + f)(3)\)[/tex]:
[tex]\[
(g + f)(3) = 5(3) + 6 = 15 + 6 = 21
\][/tex]
So, [tex]\((g + f)(3) = 21\)[/tex].
Therefore, the results are:
[tex]\[
\begin{aligned}
(g - f)(x) &= -x + 6 \\
(g \cdot f)(x) &= 6x^2 + 18x \\
(g + f)(3) &= 21
\end{aligned}
\][/tex]