б) \(x:\frac{2}{3}=3:4\);
Преобразуем пропорцию:
\(\frac{x}{\frac{2}{3}} = \frac{3}{4}\)
\(4 \cdot x = 3 \cdot \frac{2}{3}\)
\(4x = 2\)
\(x = \frac{2}{4} = \frac{1}{2} = 0,5\)
Ответ: \(x = 0,5\)