If y equals -6 when x equals 9 find x when y equals -3

The thought process here is meant to be along these lines:

y = -6 when x =9

y = -3, and -3 is half of -6. so, proportionally speaking, if -3 is half of 6, the x value that the question asks for will have to be half of 9 -- 4.5.

X would equal 12 because, to go from -6 to -3 you would need to add 3. Do the same with nine, 9 + 3 = 12.