$2+1\left(-15\right)-\left(10\right)-\left(-5\right)$

$\left(x^3-2x^2-x+5\right)+\left(4x^4-3x^2+7x-2\right)$

$\left(3a^{2}\right)+\left(3a^{2}\right)+\left(-a^{2}\right)$

$\left[\left(-19\right)\:-\:\left(-4\right)\right]\:-\:\left[\left(-18\right)\:-\:\left(-6\right)\right]$

$2a^3+5a-3-2a^3-4a$

$16x^2-24x=2$

$\left(2x\right)^3\cdot x^2\cdot x^{-7}\cdot2x^2$