$\left(\left(-5\right)+\left(-19\right)\right)-\left(\left(25\right)-\left(-23\right)\right)$

$\int\frac{1}{x^4\cdot\sqrt{x^2+16}}dx$

$3+2x=3\left(x-6\right)$

$1-\left(5-3+2\right)-\left|5-\left(6-3+1-2\right)\right|$

$\frac{3x^3}{x^2+x-2}$

$1-\left(7^3\right)$

$2\frac{8}{9}x\frac{1}{2}$