а) $$ \frac{45}{100} = \frac{5 \cdot 9}{5 \cdot 20} = \frac{9}{20} $$
б) $$ \frac{75}{1000} = \frac{25 \cdot 3}{25 \cdot 40} = \frac{3}{40} $$
в) $$ \frac{1125}{1500} = \frac{225 \cdot 5}{225 \cdot 6} = \frac{5 \cdot 1}{5 \cdot 6} = \frac{1}{6} $$
Ответ: