.125 is the answer to that question
        
             
        
        
        
"y varies directly as x" means y = kx
 
you do not know what k is yet, other than that it is some constant number.
 
Now plug in the given values, y=12 when x=4, in the equation
 
12 = 4k
 
=> k = 3
 
Now rewrite the equation with the k value you just found
 
y = 3k
 
Substitute 18 in place of x
 
y = 3(18)
 
y = 54
 
        
             
        
        
        
to find the inverse  exchange the x and y and then solve for y
y =2x^2
x =2y^2
divide by 2
x/2 = y^2
take the square root of each side
sqrt(x/2) =y
the inverse of y =2x^2  is sqrt(x/2)
 
        
                    
             
        
        
        
Answer:
I agree with the other answer 
Step-by-step explanation: