$$2t\cdot4t$$

$$\frac{\sin\left(x\right)}{1+\cos\left(x\right)}+\frac{1+\:\cos\left(x\right)}{\sin\left(x\right)}=2\csc\left(x\right)$$

$$12+12\cdot4$$

$$\frac{a}{a+1}-1$$

$$\sin x=\frac{5}{7}$$

$$2x^2-21x-27$$

$$3y^3\left(m-n\right)+4z^2\left(m-n\right)$$