The final answer is shown as 6, the initial steps first factor into prime factors (2*3^2)/(3).  The changing of 18 to (3^2)*2 is simply a feature of the software, in that all integers are prime factored. Prime factorization is a good practice because it helps identify common terms in the numerator and denominator of any fraction and therefore ensures that cancellations are properly recognized. 

It is also good to point out the 'Options' tab.  Clicking on 'Options' and changing the solution steps to 'a few steps' can be a better practice in order to avoid long solution steps which are not always useful.