\(\dfrac{3}{7}.\dfrac{9}{26}-\dfrac{1}{14}.\dfrac{1}{13}+\dfrac{6}{7}\)
\(=\left(\dfrac{3}{7}+\dfrac{6}{7}\right).\left(\dfrac{9}{26}-\dfrac{1}{13}\right).\dfrac{1}{14}\)
\(=\dfrac{9}{7}.\dfrac{7}{26}.\dfrac{1}{14}\)
\(=\dfrac{18}{14}.\dfrac{7}{26}.\dfrac{1}{14}=\dfrac{126}{5096}=\dfrac{9}{364}\)