81 2 18 90 3 20

\[ \frac{81}{90} \div \frac{2}{3} \div \frac{18}{20} = \frac{81}{90} \cdot \frac{3}{2} \cdot \frac{20}{18} = \frac{81 \cdot 3 \cdot 20}{90 \cdot 2 \cdot 18} = \frac{4860}{3240} = \frac{3}{2} = 1\frac{1}{2} \]

Ответ: \(1\frac{1}{2}\)