To factor the expression \( 8a - 18 \), we first look for the greatest common factor (GCF) of the two terms, which are \( 8a \) and \( -18 \).
The GCF of \( 8 \) and \( 18 \) is \( 2 \).
Now, we can factor out \( 2 \) from the expression:
\[ 8a - 18 = 2(4a - 9) \]
Thus, the factored form of \( 8a - 18 \) is:
\[ 2(4a - 9) \]
This is the answer as a product with a whole number greater than 1.