a) $$\frac{45}{100} = \frac{5 \cdot 9}{5 \cdot 20} = \frac{9}{20}$$
б) $$\frac{75}{1000} = \frac{25 \cdot 3}{25 \cdot 40} = \frac{3}{40}$$
в) $$\frac{1125}{150} = \frac{25 \cdot 45}{25 \cdot 6} = \frac{45}{6} = \frac{15}{2} = 7 \frac{1}{2}$$
Ответ: а) $$\frac{9}{20}$$; б) $$\frac{3}{40}$$; в) $$7 \frac{1}{2}$$