1 3 4-:6-

$$4{\frac{1}{2}}: 6{\frac{3}{4}} = {\frac{9}{2}}: {\frac{27}{4}} = {\frac{9}{2}} \cdot {\frac{4}{27}} = {\frac{9\cdot4}{2\cdot27}} = {\frac{9\cdot2\cdot2}{2\cdot9\cdot3}} = {\frac{2}{3}}$$

Ответ: 2/3