$20-1.5r+0.75$

$\left(3^5\cdot5^{-4}\right)\cdot\left(2^3\cdot3^{-4}\cdot5^6\right)$

$\left(x-3\right)\left(x+3\right)+\left(x-3\right)\left(x-1\right)$

$\left(x+15\right)\left(x+3\right)$

$-24.6+\left(14.8\right)$

$f\left(4\right)=\frac{4\left(0\right)-10}{x-2}$

$-3x^2+6x-2$