This could be answered by using the distributive property.
This is an algebra property which is done to multiply a particular term and two or more terms in a set of parentheses.
So for our problem, 6 (3 + 9):
You first, multiply 6 x 3 = 18
And multiply 6 x 9 = 56
Thus, the answer is 18 + 56 = 72
But following the order of operations, you should add first the number inside the parenthesis and then multiply it to the number outside the parenthesis but it will the same answer still. (6 x 12 = 72)