Question

If y=6 when x=9 find x when y=12

Answer 1

There is not much information here, so the function for y = 6 and x = 9 could be a lot different than what I'm going with.

y = x - 3

6 = 9 - 3

12 = x - 3

12 = 15 - 3

The value of x is equal to 15.