# How do you evaluate 9 + 7z for z=3?

Substitute $\textcolor{red}{3}$ for $\textcolor{red}{z}$ and evaluate the expression giving:
$9 + 7 \textcolor{red}{z}$ becomes:
$9 + \left(7 \cdot \textcolor{red}{3}\right) \implies 9 + 21 \implies 30$