Bài 6: Tính
a, (6\(\dfrac{4}{9}\) + 3\(\dfrac{7}{11}\)) - 4\(\dfrac{4}{9}\)
b, -1\(\dfrac{1}{3}\) - 2\(\dfrac{5}{6}\) . \(\dfrac{6}{11}\) + 3 : 5%
c, \(\dfrac{2}{3.5}\) + \(\dfrac{2}{5.7}\) + \(\dfrac{2}{7.9}\) + ... + \(\dfrac{2}{97.99}\)
d, \(\dfrac{5}{7}\)\(\dfrac{5}{11}\) + \(\dfrac{5}{7}\) . \(\dfrac{2}{11}\) - \(\dfrac{5}{7}\). \(\dfrac{14}{11}\)