$7x-y;\:x=2;\:y=5$

$3xc\left(4a-5b\right)+5mc\left(5b-4b\right)$

$\frac{4}{9}x^2-\frac{4}{12}xy+\frac{1}{16}y^2$

$\lim_{x\to8}\left(\frac{\left(x^2-2x-48\right)}{x-8}\right)$

$\left(m\:+\:7\right)\left(m\:+\:5\right)$

$x^2y'\:+\:xy\:=\:3$

$\frac{x^5-x^4+x^2-2}{x^2+1}6$