1. **State the problem:** Simplify the expression $1a + b$. 2. **Understand the terms:** Here, $1a$ means $1 \times a$, which is just $a$ because multiplying by 1 does not change the value. 3. **Simplify the expression:** Replace $1a$ with $a$: $$1a + b = a + b$$ 4. **Final answer:** The simplified form of $1a + b$ is $a + b$.