Final answer:
The symbol that replaces the question mark to make the statement true is the less than symbol (<).
Step-by-step explanation:
To determine which symbol makes the mathematical statement true, first calculate the value of each side of the potential inequality or equation.
When performing calculations, remember to follow the order of operations, also known as PEMDAS (Parentheses, Exponents, Multiplication and Division from left to right, Addition and Subtraction from left to right).
For the left side: 18 ÷ 6 + 3 = 3 + 3 = 6.
For the right side: 6 + 12 ÷ 3 = 6 + 4 = 10.
Comparing the two values, we determine that 6 is less than 10. Therefore, the correct symbol to make the statement true is < (less than).