$-2c+3a;\:a=-3;\:c=-\frac{1}{2}$

$\frac{\left(+4\right).\left(-5\right)}{\left(-4\right)}$

$\left(xy-2z\right)^3$

$-8\left(-7\right)-60$

$\frac{-2}{3}rt\cdot\frac{-5}{4}r^2t^3\cdot\frac{-1}{5}rt^2$

$\lim_{x\to0}\left(\frac{x-2}{x^2-2}\right)$

$\frac{dy}{dx}\left(x^2+ysin\left(x\right)=2y\right)$