$\frac{27xy^2}{36xz}$

$6-2\cdot\left(-3\right)-\left(5-2\cdot\left(-5\right)+3\right)$

$\left(4x^2+4x=5\right)^2$

$x^2+x^2+x^2$

$7\left(-10\right)\left(2\right)\:$

$\frac{d}{dx}sen\left(xy\right)=xy$

$\frac{\sin\left(x\right)-\csc\left(x\right)}{\csc\left(x\right)}=-\cos^2\left(x\right)$