Question 234104
{{{(3a-3y)/(3a-3y-ab+by)}}} * {{{(b^2-9)/(6b+18)}}} 
:
{{{(3(a-y))/(3(a-y)-b(a-y))}}} * {{{((b-3)(b+3))/(6(b+3))}}}
:
Factor out (a-y) in the denominator
{{{(3(a-y))/((a-y)(3-b)))}}} * {{{((b-3)(b+3))/(6(b+3))}}}
:
Cancel (a-y) & (b+3)
{{{3/((3-b)))}}} * {{{((b-3))/6)}}}
:
Cancel 3 into 6
{{{1/((3-b)))}}} * {{{((b-3))/2)}}}
:
Use -1 to make (b-3)
{{{1/(-1(b-3)))}}} * {{{((b-3))/2)}}}
:
Cancel (b-3)
{{{1/((-1))}}} * {{{1/2)}}}
:
-1 * {{{1/2}}} = {{{-1/2}}}