\(\dfrac{-1}{8}+\dfrac{-5}{16}=\dfrac{-1}{8}-\dfrac{5}{16}=-\dfrac{7}{16}\)
\(\dfrac{-3}{8}-\dfrac{1}{-3}=\dfrac{-3}{8}-\dfrac{-1}{3}=\dfrac{-3}{8}+\dfrac{1}{3}=-\dfrac{1}{24}\)
\(\dfrac{2}{3}\times\dfrac{-5}{7}=\dfrac{2\cdot\left(-5\right)}{3\cdot7}=-\dfrac{10}{21}\)