$5a-6b+8c+9a-20c+6b+c+5b$

$\frac{senxcosx}{tanx}=2$

$\frac{\frac{21}{17}+3}{4}+\frac{\frac{21}{17}+6}{3}=2\left(\frac{21}{17}+1\right)$

$\ \left(2\left(2\right)-5\right)\left(-3\left(2\right)+4\right)\:$

$-11\:-\:\left(-4\right)$

$\sqrt{\frac{x}{\sqrt{x\:+2}}}$

$\left(4a^3-50ab^2-6a^2b^3\right)entr\left(-2\right)$