\[ \begin{align*} \dfrac{18}{27} \times \dfrac{12}{9} &= \dfrac{18\times 12}{27\times 9} \\ &= \dfrac{216}{243} \\ &= \dfrac{72}{81} \\ &= \dfrac{24}{27} \\ &= \dfrac{8}{9} \end{align*} \] \[ \begin{align*} \dfrac{14}{21} \times \dfrac{35}{42} &= \dfrac{14\times 35}{21\times 42} \\ &= \dfrac{490}{882} \\ &= \dfrac{5}{9} \end{align*} \] \[ \begin{align*} \dfrac{20}{30} \times \dfrac{45}{50} &= \dfrac{900}{1500} \\ &= \dfrac{3}{5} \end{align*} \] \[ \begin{align*} \dfrac{24}{36} \times \dfrac{18}{16} &= \dfrac{432}{576} \\ &= \dfrac{3}{4} \end{align*} \]