Question 511612
{{{(4/5-10/12-5/6) / (14/8+10/21)}}} 
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Numerator:
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{{{4/5 -10/12 - 5/6 = 48/60 -50/60 -50/60 = -52/60 = -13/15}}}
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Denominator:
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{{{14/8+10/21 = (21*14 + 8*10)/(8*21) = 187/84}}}
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{{{ (-13/15) / (187/84)  = (-13/15)*(84/187) = -(364/935) }}}