Answer
$0$ is the solution.
Work Step by Step
To simplify this expression, we refer to the order of operations, represented by the acronym PEMDAS, we evaluate parentheses first (starting with inner parentheses), then exponents and radicals, then multiplication and division, and, finally, addition and subtraction.
Therefore, we evaluate the parentheses first. Inside the parentheses, there is an exponent, so we will evaluate the exponent first:
$$3(12 \div 4 - 3)^2$$
Next, we do the division within the parentheses:
$$3(3 - 3)^2$$
Do the subtraction inside the parentheses:
$$3(0)^2$$
Evaluate the exponent first:
$$3(0)$$
Multiply:
$0$ is the solution.