a) $$\frac{4}{10} = \frac{2}{5}$$
б) $$\frac{36}{30} = \frac{6}{5}$$
в) $$\frac{15\cdot24\cdot17}{8\cdot34\cdot15} = \frac{24\cdot17}{8\cdot34} = \frac{3\cdot17}{34} = \frac{3}{2}$$
г) $$\frac{16a}{12b} = \frac{4a}{3b}$$