$B = 5[ \dfrac{12 - \dfrac{12}{7} - \dfrac{12}{289} - \dfrac{12}{85}}{4 - \dfrac{4}{7} - \dfrac{4}{289} - \dfrac{4}{85}} : \dfrac{5 + \dfrac{5}{13} + \dfrac{5}{169}+ \dfrac{5}{91}}{6 + \dfrac{6}{13} + \dfrac{6}{169}+ \dfrac{6}{91}} ]. \dfrac{158158158}{711711711}$
` ⇔B = 5.[` $\dfrac{12.(1 - \dfrac{1}{7} - \dfrac{1}{289} - \dfrac{1}{85})}{4 . (1 - \dfrac{1}{7} - \dfrac{1}{289} - \dfrac{1}{85})} : \dfrac{5 . (1 + \dfrac{1}{13} + \dfrac{1}{169} + \dfrac{1}{91})}{6 . (1 + \dfrac{1}{13} + \dfrac{1}{169} + \dfrac{1}{91})}$ `]` . $\dfrac{158}{711}$
$⇔B = 5.[ \dfrac{12}{4} : \dfrac{5}{6} ] . \dfrac{158}{711}$
`⇔B = 5. ` $\dfrac{18}{5}$ . $\dfrac{158}{711}$
$⇔B = 18 . \dfrac{158}{711}$
$⇔B =\dfrac{2844}{711}$
$⇔B =4$
