a, \(12,5.\left(\dfrac{-5}{7}\right)+1,5.\left(\dfrac{-5}{7}\right)\)

\(=\left(\dfrac{-5}{7}\right).\left(12,5+1,5\right)=\left(\dfrac{-5}{7}\right).14=-10\)

b, \(\left(\dfrac{-2}{5}-\dfrac{3}{7}\right):\dfrac{4}{5}+\left(\dfrac{-1}{5}+\dfrac{3}{7}\right):\dfrac{4}{5}\)

\(=\left[\left(-\dfrac{2}{5}-\dfrac{1}{5}\right)+\left(\dfrac{-3}{7}+\dfrac{3}{7}\right)\right]:\dfrac{4}{5}\)

\(=\left(\dfrac{-3}{5}+0\right):\dfrac{4}{5}=\dfrac{-3}{5}.\dfrac{5}{4}=\dfrac{-3}{4}\)

c, \(12.\left(\dfrac{-2}{3}\right)^2+\dfrac{4}{3}\)

\(=12.\left(\dfrac{-2^2}{3^2}\right)+\dfrac{4}{3}=12.\left(\dfrac{4}{9}\right)+\dfrac{4}{3}=\dfrac{16}{3}+\dfrac{4}{3}=5\)

d, \(1:\left(\dfrac{2}{3}-\dfrac{3}{4}\right)^2=1:\left(\dfrac{-1}{12}\right)^2=1:\dfrac{1}{144}=144\)

e, \(15.\left(\dfrac{-2}{3}\right)^2-\dfrac{7}{3}\)

\(=15.\dfrac{4}{9}-\dfrac{7}{3}=\dfrac{20}{3}-\dfrac{7}{3}=\dfrac{13}{3}\)