15/20 : 150/200 : 2/3 =

$$\frac{15}{20} : \frac{150}{200} : \frac{2}{3} = \frac{15}{20} \cdot \frac{200}{150} \cdot \frac{3}{2} = \frac{3}{4} \cdot \frac{4}{3} \cdot \frac{3}{2} = 1 \cdot \frac{3}{2} = \frac{3}{2}$$