The statement "y varies inversely as x means that when x increases, y decreases by the same factor. In other words, the expression xy is constant :
x*y = k
k is the variation constant.
Just substitute the values in that formula :
16*9 = 4*4*9 = 172.
So the variation constant here is 172.
In order to find the equation of variation of y, you should change the equation i gave you.
y = k/x
y= 172/x
Hope this helps !
Photon
