Question: solve $3(a)$
1. **State the problem:** Solve the expression or equation labeled as $3(a)$. Since the user only wrote "3(a)", we assume it refers to evaluating or simplifying the expression $3 \times a$.
2. **Formula used:** Multiplication of a number and a variable is given by $3 \times a = 3a$.
3. **Explanation:** Multiplying the constant $3$ by the variable $a$ results in the product $3a$.
4. **Final answer:** The simplified form of $3(a)$ is $3a$.
This completes the solution for $3(a)$.