To add or subtract expressions, expand them to make their denominators the same. Least common multiple of $\left(x-1\right)\left(x+3\right)$ and $\left(1-x\right)\left(x+2\right)$ is $\left(x-1\right)\left(x+2\right)\left(x+3\right)$. Multiply $\frac{x}{\left(x-1\right)\left(x+3\right)}$ times $\frac{x+2}{x+2}$. Multiply $\frac{x-3}{\left(1-x\right)\left(x+2\right)}$ times $\frac{-\left(x+3\right)}{-\left(x+3\right)}$.
Since $\frac{x\left(x+2\right)}{\left(x-1\right)\left(x+2\right)\left(x+3\right)}$ and $\frac{\left(x-3\right)\left(-1\right)\left(x+3\right)}{\left(x-1\right)\left(x+2\right)\left(x+3\right)}$ have the same denominator, add them by adding their numerators.
To add or subtract expressions, expand them to make their denominators the same. Least common multiple of $\left(x-1\right)\left(x+2\right)\left(x+3\right)$ and $x+2$ is $\left(x-1\right)\left(x+2\right)\left(x+3\right)$. Multiply $\frac{1}{x+2}$ times $\frac{\left(x-1\right)\left(x+3\right)}{\left(x-1\right)\left(x+3\right)}$.
Since $\frac{2x+9}{\left(x-1\right)\left(x+2\right)\left(x+3\right)}$ and $\frac{\left(x-1\right)\left(x+3\right)}{\left(x-1\right)\left(x+2\right)\left(x+3\right)}$ have the same denominator, subtract them by subtracting their numerators.
To add or subtract expressions, expand them to make their denominators the same. Least common multiple of $\left(x-1\right)\left(x+3\right)$ and $\left(1-x\right)\left(x+2\right)$ is $\left(x-1\right)\left(x+2\right)\left(x+3\right)$. Multiply $\frac{x}{\left(x-1\right)\left(x+3\right)}$ times $\frac{x+2}{x+2}$. Multiply $\frac{x-3}{\left(1-x\right)\left(x+2\right)}$ times $\frac{-\left(x+3\right)}{-\left(x+3\right)}$.
Since $\frac{x\left(x+2\right)}{\left(x-1\right)\left(x+2\right)\left(x+3\right)}$ and $\frac{\left(x-3\right)\left(-1\right)\left(x+3\right)}{\left(x-1\right)\left(x+2\right)\left(x+3\right)}$ have the same denominator, add them by adding their numerators.
To add or subtract expressions, expand them to make their denominators the same. Least common multiple of $\left(x-1\right)\left(x+2\right)\left(x+3\right)$ and $x+2$ is $\left(x-1\right)\left(x+2\right)\left(x+3\right)$. Multiply $\frac{1}{x+2}$ times $\frac{\left(x-1\right)\left(x+3\right)}{\left(x-1\right)\left(x+3\right)}$.
Since $\frac{2x+9}{\left(x-1\right)\left(x+2\right)\left(x+3\right)}$ and $\frac{\left(x-1\right)\left(x+3\right)}{\left(x-1\right)\left(x+2\right)\left(x+3\right)}$ have the same denominator, subtract them by subtracting their numerators.