Thực hiện phép tính ( hợp lí nếu có ) :
a) ( \(\frac{1}{4}\) + \(\frac{-5}{13}\) ) + ( \(\frac{2}{11}\) + \(\frac{-8}{13}\) + \(\frac{3}{4}\) )
b) ( \(\frac{21}{31}\) + \(\frac{-16}{7}\) ) + ( \(\frac{44}{53}\) + \(\frac{10}{31}\) ) + \(\frac{9}{53}\)
c) \(\frac{\frac{9}{45}-\frac{4}{13}-\frac{1}{3}}{\frac{3}{13}-\frac{1}{15}+\frac{2}{3}}\)