Question 182399
Assuming this is what your expression looks like:
{{{ 15x(x-y)/5x^3y(x-y) }}}
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You can cancel out the (x-y) elements on top & bottom, leaving you with:
{{{ 15x / 5x^3y }}}
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From here you can reduce each element independently, leaving you with:
{{{ 3 / x^2y }}}
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Which is answer <b>B</b>.  Hope that helps.  Let me know if any step is unclear.

- Joe