a: \(=\dfrac{7}{12}\cdot12=7\)
b: \(=\dfrac{3}{8}\cdot\dfrac{25}{7}\cdot56\cdot\left(-4\right)=-300\)
c: \(=\dfrac{3}{7}\cdot\dfrac{7}{3}\cdot\dfrac{2}{5}\cdot20\cdot\dfrac{19}{72}=8\cdot\dfrac{19}{72}=\dfrac{19}{9}\)
d: \(=\dfrac{1}{3}\left(\dfrac{4}{5}+\dfrac{6}{5}\right)=\dfrac{2}{3}\)