# y varies inversely with x. Find the inverse variation equation if x = 12 when y = -18

I'm very surprised that you would be given a problem like that and not even be told what "inverse variation" means! If x and y have an "inverse variation" then $y= \frac{k}{x}$ which is the same as xy= k. Knowing that "x= 12 when y= -18" lets you calculate k.