Помогите плиз срочно 3

( $( \frac{3}{x+4}+ \frac{6x}{ x^{2} +x-12}- \frac{1}{x-3}): \frac{8x-13}{ x^{2} -16}= \\ =( \frac{3}{x+4}- \frac{1}{x-3}+ \frac{6x}{ x^{2} +x-12})*\frac{x^{2} -16}{ 8x-13}= \\ =(\frac{3*(x-3)-(x+4)+6x}{ x^{2} +x-12})*\frac{x^{2} -16}{ 8x-13}= \\ =\frac{3x-9-x-4+6x}{ x^{2} +x-12}*\frac{x^{2} -16}{ 8x-13}= \\ =\frac{8x-13}{ x^{2} +x-12}*\frac{x^{2} -16}{ 8x-13}=\frac{x^{2} -16}{ x^{2} +x-12}$ )