b) $ \frac{\frac{3}{7} - \frac{3}{11} + \frac{3}{13}}{\frac{5}{7} - \frac{5}{11} + \frac{5}{13}} + \frac{\frac{1}{2} - \frac{1}{3} + \frac{1}{4}}{\frac{5}{4} - \frac{5}{6} + \frac{5}{8}}$
= $ \frac{3.(\frac{1}{7} - \frac{1}{11} + \frac{1}{13} )}{5.(\frac{1}{7} - \frac{1}{11} + \frac{1}{13} )} + \frac{\frac{1}{2}(\frac{1}{2} - \frac{1}{3} + \frac{1}{4} )}{\frac{1}{2} - 5 ( \frac{1}{4} - \frac{1}{6} + \frac{1}{8} )}$
= $ \frac{3}{5} + \frac{\frac{1}{4} - \frac{1}{6} + \frac{1}{8}}{\frac{5}{2}.(\frac{1}{4}-\frac{1}{6}+\frac{1}{8})}$
= $ \frac{3}{5} + \frac{\frac{1}{5}}{2}$
= $ \frac{3}{5} + 1 . \frac{2}{5} = \frac{3}{5} + \frac{2}{5} = \frac{5}{5} = 1$