Thực hiện phép tính: a) (6\(\dfrac{4}{9}\) + 3 \(\dfrac{7}{11}\)) - 4\(\dfrac{4}{9}\) b) \(\dfrac{1}{7}\). \(\dfrac{1}{5}\) + \(\dfrac{1}{7}\) . \(\dfrac{2}{5}\) + \(\dfrac{1}{7}\) .\(\dfrac{4}{5}\)
c) 25% - 1\(\dfrac{1}{2}\) . (-2019)o + 0,5 . \(\dfrac{12}{5}\)