The function provided at the top is:

$f(x) = 3(-2x + 7)$

Let's evaluate this function at different values of $x$ as requested:

a) $f(-7)$:

$f(-7) = 3(-2(-7) + 7)$ $f(-7) = 3(14 + 7) = 3 \times 21 = 63$

b) $f(13)$:

$f(13) = 3(-2(13) + 7)$ $f(13) = 3(-26 + 7) = 3 \times (-19) = -57$

c) $f(11)$:

$f(11) = 3(-2(11) + 7)$ $f(11) = 3(-22 + 7) = 3 \times (-15) = -45$

d) $f(-8)$:

$f(-8) = 3(-2(-8) + 7)$ $f(-8) = 3(16 + 7) = 3 \times 23 = 69$

If you have any questions or need further details, feel free to ask!

Here are five related questions to expand your understanding:

1. How would you rewrite $f(x)$ in a simplified form?
2. What is the slope of the linear function $f(x)$?
3. How does the graph of $f(x)$ look based on its equation?
4. What happens to $f(x)$ as $x$ becomes very large or very small?
5. How would you find the x-intercept of $f(x)$?

Tip: When evaluating functions, always substitute values for $x$ carefully, making sure to apply any negative signs properly!