Bài 8:
a: \(=\dfrac{5}{7}-\dfrac{3}{5}=\dfrac{25-21}{35}=\dfrac{4}{35}\)
b: \(=\dfrac{-3}{7}+\dfrac{2}{9}=\dfrac{-27+14}{63}=\dfrac{-13}{63}\)
c: \(=\dfrac{-5}{11}+\dfrac{6}{7}=\dfrac{-35+66}{77}=\dfrac{31}{77}\)
d: \(=\dfrac{334}{335}-\dfrac{4}{335}=\dfrac{330}{335}=\dfrac{66}{67}\)