$\left(21x^5-35x^2y^2+6x^3y-10y^3\right)$

$4n^2-32n=-4n^2-14$

$x^2+3x+4x+12$

$6.9=\tan\left(24\right)-\left(4.9\cdot\left(\frac{24}{18.121\cdot\cos\left(x\right)}\right)\right)$

$12\cdot 21$

$\lim_{x\to\infty}\left(sin\left(\frac{3\pi}{x}\right)\right)$

$\left(-4\right)\cdot2\cdot\left(-3\right)+8\cdot\left(-5\right)-\left(-7\right)$