$$\frac{2}{3}\left(3x\right)^{\frac{1}{3}}\left(3x^{\frac{2}{3}}\right)$$

$$\ln\left(\frac{x}{x-9}\right)+\ln\left(\frac{x+9}{x}\right)-\ln\left(x^2-81\right)$$

$$\left(x+7\right).\left(x-4\right)$$

$$4z+8y-2t+5t+8z-6y$$

$$62x^2+x-28$$

$$4x-9\le19$$

$$\frac{x^{10}}{x^4}$$