If they are proportional, then y/x should always be the same. 
So 9/2= 4.5
We need to find the y value at x=3 to make y/x equal 4.5
4.5 = y/3
y = 4.5*3 = 13.5
        
             
        
        
        
Answer:
Simplify the expression.
12xy−72yexponent 2 -6x
Step-by-step explanation:
got it from mathaway