The answer is 11.66 or 11.67 depending on how you round the decimal
        
             
        
        
        
Replace u,x and y withyour values
u+xy=2+9*6=2+54=56
        
                    
             
        
        
        
                                  <u> 4 x²  =  64</u>
Divide each side by  4 :     x² = 16
Take the square root 
of each side:                     x = √16
                                   x = <em>+ 4</em>
and
                                   x = <em>- 4</em> .
        
                    
             
        
        
        
A factor of 24 but not 2 it would be 3