To add or subtract expressions, expand them to make their denominators the same. Least common multiple of $x+3$ and $\left(x-4\right)\left(x+3\right)$ is $\left(x-4\right)\left(x+3\right)$. Multiply $\frac{2\left(x+4\right)}{x+3}$ times $\frac{x-4}{x-4}$.
Since $\frac{2\left(x+4\right)\left(x-4\right)}{\left(x-4\right)\left(x+3\right)}$ and $\frac{x^{2}+3x-24}{\left(x-4\right)\left(x+3\right)}$ 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 $x+3$ and $\left(x-4\right)\left(x+3\right)$ is $\left(x-4\right)\left(x+3\right)$. Multiply $\frac{2\left(x+4\right)}{x+3}$ times $\frac{x-4}{x-4}$.
Since $\frac{2\left(x+4\right)\left(x-4\right)}{\left(x-4\right)\left(x+3\right)}$ and $\frac{x^{2}+3x-24}{\left(x-4\right)\left(x+3\right)}$ have the same denominator, subtract them by subtracting their numerators.