Answer
$$6$$
Work Step by Step
In order to solve this problem, we follow order of operations. (Recall, we use the abbreviation PEDMAS to indicate the correct order.) Doing this, we find:
$$ 18\div \:3\cdot \:2-6^2\div \left(2+4\right)\\ 18\div \:3\cdot \:2-36\div \:6\\ 12-36\div \:6\\ 12-6\\ 6$$