$12-\left(+16-11+3\right)-\left(-3+5\right)$

$\lim_{x\to0}\left(e^{-2}ln5x^2\right)$

$\frac{dx}{dt}=-5x+3$

$\lim_{x\to6}\left(\frac{10x^2-52x\:+48}{4x^2+2x-156}\right)$

$\lim_{x\to\infty}\left(\frac{2n}{x+1}\right)$

$\frac{csc\left(x\right)\:cos\left(x\right)\:}{tan\left(x\right)+cot\left(x\right)}=cos^2\left(x\right)$

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