Question 1008308
Using the "fraction bar" in place of the division operator,

{{{(9-m^2n^-2)/(3-m^1n^-1)}}}


Changing to all positive exponents,
{{{(9-m^2/n^2)/(3-m^1/n)}}}


Simplest common denominator is  {{{n^2/n^2}}}...

{{{((9-m^2/n^2)/(3-m^1/n))(n^2/n^2)}}}


{{{highlight((9n^2-m^2)/(3n^2-mn))}}}-----THIS is the best final result.


There might be one further step, but reducing the fractional expression could change some of its meaning.


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Possible next steps,
{{{((3n-m)(3n+m))/(n(3n-m))}}}
and then
{{{(cross((3n-m))(3n+m))/(n*cross((3n-m)))}}}

{{{highlight_green((3n+m)/n)}}}-------but like said already, this changes the meaning of the expression.