Question 156270
Assume the problem is:
:

{{{4/x + 1/(2x)}}}
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{{{1/(3x) - 3/(4x)}}}
Place each over a common denominator
{{{(2(4)+1)/(2x)}}}
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{{{(4(1)-3(3))/(12x)}}}
:
Do the math on the numerators:
{{{9/(2x)}}}
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{{{(-5)/(12x)}}}
invert the dividing fraction and multiply:
{{{9/(2x)}}} * {{{-(12x)/5}}}
Cancel 2x into 12x
9 * {{{-6/5}}} = {{{-54/5}}}