$\frac{3\left(a-b\right)}{9}\:+\:\frac{4}{9}b$

$\lim_{x\to5}\left(\frac{\cos\left(x\right)\ln\left(x-5\right)}{\ln\left(e^x-e^5\right)}\right)$

$\frac{21x^5y^7}{14x^3y^8}$

$\frac{d^2}{dx^2}\left(3x-x^2\cos\left(x\right)\right)$

$25x^2+200x+400$

$100+x+0.01x^2=700\:$

$\int\left(tan^{-1}\right)\left(x^8\right)dx$