a) \(\left(\dfrac{1}{4}+\dfrac{1}{12}\right):\dfrac{1}{13}\)
\(=\left(\dfrac{3}{12}+\dfrac{1}{12}\right):\dfrac{1}{13}\)
\(=\dfrac{4}{12}\times13\)
\(=\dfrac{1}{3}\times13\)
\(=\dfrac{13}{3}\)
b) \(\dfrac{3}{5}:\dfrac{2}{9}-\dfrac{1}{10}\)
\(=\dfrac{3}{5}\times\dfrac{9}{2}-\dfrac{1}{10}\)
\(=\dfrac{27}{10}-\dfrac{1}{10}\)
\(=\dfrac{26}{10}\)
\(=\dfrac{13}{5}\)