$75\int_0^{30}\left(e^{-\frac{x}{50}}\right)dx$

$\frac{dy}{dx}=x^3\left(9-x^2\right)$

$\left(3a^3+9b^3\right)$

$4+\frac{6}{2}$

$\left(+2\right)-\left(+8\right)+\left(-5\right)-\left(-3\right)-\left(-1\right)$

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

$2^2.5^2.7$