To factor the expression \( 36 - 27x \), we can first look for the greatest common factor (GCF) of the two terms, which are \( 36 \) and \( -27x \).
- The GCF of \( 36 \) and \( 27 \) is \( 9 \).
- We can factor out \( 9 \):
\[ 36 - 27x = 9(4 - 3x) \]
So, the expression factored completely is:
\[ \boxed{9(4 - 3x)} \]