\(\dfrac{old\,\,numerator}{old\,\,unique\,\,denominator} \pm\)
\(\dfrac{old\,\, numerator}{old\,\,unique\,\, denominator} \,\, ...\)
\(\longrightarrow\)
\(\dfrac{LCM\,\,of\,\,old\,\,unique\,\,denominators/old\,\,unique\,\, denominator * old\,\,numerator}{LCM\,\,of\,\,old\,\,unique\,\,denominators} \pm\)
\(\dfrac{LCM\,\,of\,\,old\,\,unique\,\,denominators/old\,\,unique\,\, denominator * old\,\,numerator}{LCM\,\,of\,\,old\,\,\,\,unique\,\,denominators}\,\, ...\)
\(\longrightarrow\)
\(\dfrac{midway\,\,numerator}{LCM\,\,of\,\,old\,\, unique\,\, denominators} \pm \dfrac{midway\,\,numerator}{LCM\,\,of\,\,old\,\,unique\,\,denominators}\,\, ... = \)
\(\dfrac{new\,\,numerator}{LCM\,\,of\,\,old\,\,unique\,\,denominators}\)
Ex.
\(\dfrac{2}{4} - \dfrac{3}{6} \longrightarrow\)
\(\dfrac{12/4 * 2}{12} - \dfrac{12/6 * 3}{12} \longrightarrow \dfrac{6}{12} - \dfrac{6}{12} = 0\)
