\(=\left\{\left[\left(\dfrac{1}{25}-\dfrac{3}{5}\right)^2\cdot\dfrac{125}{49}\right]\cdot\dfrac{5}{6}\right\}-\dfrac{1}{6}\)
\(=\left\{\left[\dfrac{196}{625}\cdot\dfrac{125}{49}\right]\cdot\dfrac{5}{6}\right\}-\dfrac{1}{6}\)
\(=\dfrac{4}{5}\cdot\dfrac{5}{6}-\dfrac{1}{6}=\dfrac{3}{6}=\dfrac{1}{2}\)