Rút gọn các phân số sau

$\frac{2.\cancel{3}.\cancel{5}}{\cancel{3}.\cancel{5}.7}=\frac{2}{7};\frac{12.(-25)}{30.18}=-\frac{\cancel{2}.\cancel{6}.\cancel{5}.5}{\cancel{5}.\cancel{2}\mathrm{.3.3.}\cancel{6}}=-\frac{5}{9}$

$a)\frac{(-2).7}{7.5};\begin{array}{cccc}& & & \end{array}b)\frac{3.(-5)}{15.(-6)};\begin{array}{cccc}& & & \end{array}c)\frac{(-6).7}{(-7).(-8)}$

$d)\frac{9.(-13)}{13.(-12)};\begin{array}{ccc}& & \end{array}e)\frac{(-21).(-5)}{15.(-7)};\begin{array}{cccc}& & & \end{array}f)\frac{\mathrm{32.9.11}}{\mathrm{12.24.22}}$