$-15-\left(-6\right)+\left(-7\right)-\left(3\right)$

$\frac{2x-1}{x-7}\le1$

$\frac{\left(-30+19i\right)x^5}{\left(-4+9i\right)x^2}$

$\int\left(5x^2-50x+30\right)^7\left(x-5\right)dx$

$\left(3-7\right)^2+\left(3-4\right)^3+\left(-3\right)^3$

$\lim_{x\to9}\left(\frac{\left|36-4x\right|}{9-x}\right)$

$4-12-28$