a: \(=\left(\dfrac{2}{5}-\dfrac{2}{5}\right)+\left(\dfrac{5}{4}+\dfrac{5}{4}\right)-\dfrac{5}{2}=\dfrac{10}{4}-\dfrac{5}{2}=0\)
b: \(=\left(-\dfrac{2}{11}-\dfrac{9}{11}\right)+\left(\dfrac{6}{7}+\dfrac{1}{7}\right)+\left(\dfrac{1}{2}+\dfrac{1}{3}\right)=\dfrac{5}{6}\)
c: \(=\dfrac{7}{19}\left(\dfrac{5}{13}+\dfrac{8}{13}-3\right)=\dfrac{7}{19}\cdot\left(-2\right)=-\dfrac{14}{19}\)
d: \(=\dfrac{12}{11}+\dfrac{9}{22}\left(\dfrac{7}{15}+\dfrac{8}{15}\right)=\dfrac{12}{11}+\dfrac{9}{22}=\dfrac{24+9}{22}=\dfrac{33}{22}=\dfrac{3}{2}\)