18) (6 8 3 - 16 ): 32

18) $$(\frac{6}{8} - \frac{3}{16}) : 32$$

$$(\frac{6}{8} - \frac{3}{16}) : 32 = (\frac{6 \cdot 2}{8 \cdot 2} - \frac{3}{16}) : 32 = (\frac{12}{16} - \frac{3}{16}) : 32 = \frac{9}{16} : 32 = \frac{9}{16} : \frac{32}{1} = \frac{9}{16} \cdot \frac{1}{32} = \frac{9}{16 \cdot 32} = \frac{9}{512}$$

Ответ: $$\frac{9}{512}$$