Question 94366
If the problem should be:
{{{(((2x-6)/21)/((5x-15)/12))}}}
 {{{(((2*(x-3))/21)/(5*(x-3)/12))}}}  [factor whenever possible]
 {{{((2*(x-3))/21)*(12/(5*(x-3)))}}}  [Multiply by flipping the denominator]
 {{{(2/21)*(12/5)}}}  [cancel wherever possible]
{{{(2/7)*(4/(5))))}}} 
 {{{(8/35)}}}