Question 672729
Create a common denominator when adding or subtracting
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Is this {{{2/7 + 3/5 + 1/3}}}?  or {{{2/4+3/5-1/3}}}
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Either way, use 7*5*3 = 105 as the common denominator
so, 
{{{(2/7)(15/15) + (3/5)(21/21)}}} + or - {{{(1/3)(35/35)}}}
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{{{(30/105) + (63/105)}}} + or - {{{(35/105)}}}

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