8 Which expression is equivalent to 5(3x + 9)?

To find the expression equivalent to \(5(3x + 9)\), we need to distribute the \(5\) across both terms inside the parentheses:

\[
5(3x + 9) = 5 \cdot 3x + 5 \cdot 9
\]

Calculating each part, we have:

\[
5 \cdot 3x = 15x
\]
\[
5 \cdot 9 = 45
\]

Now, combine the two results:

\[
5(3x + 9) = 15x + 45
\]

Thus, the equivalent expression is:

\[
\text{c) } 15x + 45
\]