40 20 3 / 50 5 4 =

\( \frac{40}{50} : \frac{20}{5} : \frac{3}{4} = \frac{40}{50} \times \frac{5}{20} \times \frac{4}{3} = \frac{40 \times 5 \times 4}{50 \times 20 \times 3} = \frac{800}{3000} = \frac{4}{15} \)

Ответ: \( \frac{4}{15} \)