Verified Answer :

The answer is 

x (x² + 5x + 6) 

-------------------- 
x ( x + 3) 

( x + 3 ) (x + 2) 
--------------------- 
x + 3 

x + 2

The given polynomial is :

\(x^{3}+5x^{2}+6x\)

One factor is given as : \(x^{2} +3x\) or \(x(x+3)\)

So, now solving this for 2nd factor, we get,            

\(x(x^{2}+5x+6 )\)          

\(x[(x^{2}+3x+2x+6)]\)          

\(x(x+3)(x+2)\)              

Hence, the second factor is (x+2)