To find the answer, you'll have to do the inverse operation of what is shown. So in you're case, the inverse operation will be multiplication, since the original one is a division:
x / 12 = -6 → we take 12 to the right side of the equation
x = -6 * 12 → we do the I.O.* of "÷ 12" by solving -6 * 12
x = -72 → final answer
To prove your answer:
-72 / 12 = -6
Hope it helped,
BioTeacher101
(If you have any questions, feel free to ask them in the comments)