1. The problem is to simplify the expression $6a - 3b$ using identities. 2. This expression is a linear combination of terms and does not directly match common algebraic identities like the difference of squares or perfect square trinomials. 3. However, we can factor out the greatest common factor (GCF) from the terms. 4. The GCF of $6a$ and $3b$ is $3$. 5. Factoring out $3$, we get: $$6a - 3b = 3(2a - b)$$ 6. This is the simplified form using factoring by identity (factoring out the GCF). 7. There are no further simplifications possible unless values for $a$ and $b$ are given. Final answer: $$6a - 3b = 3(2a - b)$$