Problem
If $f(x)=5 x$ and $g(x)=3 x-6$, find $(f g)(x)$. \[ (\mathrm{fg})(\mathrm{x})=\square \]
Solution
Step 1 ：\(f(g(x)) = f(3x - 6)\)
Step 2 ：\(f(g(x)) = 5(3x - 6)\)
Step 3 ：\(f(g(x)) = 15x - 30\)
Step 4 ：\(\boxed{f(g(x)) = 15x - 30}\)
