To solve the equation \( 5 \cdot (12 - x) - 20 = 30 \), follow these steps:

1. Distribute the 5 inside the parentheses:
\[
5 \cdot 12 - 5 \cdot x - 20 = 30
\]
Simplify the multiplication:
\[
60 - 5x - 20 = 30
\]

2. Combine like terms on the left side:
\[
40 - 5x = 30
\]

3. Isolate the term with \( x \) by subtracting 40 from both sides:
\[
40 - 5x - 40 = 30 - 40
\]
Simplify:
\[
-5x = -10
\]

4. Solve for \( x \) by dividing both sides by -5:
\[
x = \frac{-10}{-5}
\]
Simplify:
\[
x = 2
\]

So, the solution to the equation is \( x = 2 \).