81 2 18 / 90 3 20 =

\( \frac{81}{90} : \frac{2}{3} : \frac{18}{20} = \frac{81}{90} \times \frac{3}{2} \times \frac{20}{18} = \frac{81 \times 3 \times 20}{90 \times 2 \times 18} = \frac{4860}{3240} = \frac{3}{2} \)

Ответ: \( \frac{3}{2} \)