\(a)\) \({\left( {\displaystyle{5 \over 7}{x^2}y} \right)^3}:{\left( {\displaystyle{1 \over 7}xy} \right)^3}\) \( = {\left( {\displaystyle{5 \over 7}{x^2}y:{1 \over 7}xy} \right)^3} = {\left( {5x} \right)^3} = 125{x^3}\)
\(b)\) \({\left( { - {x^3}{y^2}z} \right)^4}:{\left( { - x{y^2}z} \right)^3}\) \( = {x^{12}}{y^8}{z^4}:\left( { - {x^3}{y^6}{z^3}} \right) = - {x^9}{y^2}z\)
