\[x^{2}(2x + 7y) - x^{2}(3x - 5y) =\]
\[= x^{2}\left( 2x + 7y - (3x - 5y) \right) =\]
\[= x^{2}(2x + 7y - 3x + 5y) =\]
\[= x^{2}( - x + 12y).\]