\(\dfrac{3}{7}.\dfrac{9}{26}-\dfrac{1}{13}-\dfrac{1}{7}\)
\(=\dfrac{27}{182}-\dfrac{1}{13}-\dfrac{1}{7}\)
\(=\dfrac{27}{182}-\dfrac{14}{182}-\dfrac{1}{7}\)
\(=\dfrac{1}{14}-\dfrac{1}{7}\)
\(=\dfrac{1}{14}-\dfrac{2}{14}=\dfrac{-1}{14}\)
= 27/182 - 14/182 - 26/182
= -13/182 = -1/14