Add $ \dfrac{2}{x} $ and $ \dfrac{7}{x-8} $ to get $ \dfrac{ \color{purple}{ 9x-16 } }{ x^2-8x }$.

To add raitonal expressions, both fractions must have the same denominator.
We can create a common denominator by multiplying the first fraction by $ \color{blue}{ x-8 }$ and the second by $\color{blue}{ x }$.

$$ \begin{aligned} \frac{2}{x} + \frac{7}{x-8} & = \frac{ 2 \cdot \color{blue}{ \left( x-8 \right) }}{ x \cdot \color{blue}{ \left( x-8 \right) }} + \frac{ 7 \cdot \color{blue}{ x }}{ \left( x-8 \right) \cdot \color{blue}{ x }} = \\[1ex] &=\frac{ \color{purple}{ 2x-16 } }{ x^2-8x } + \frac{ \color{purple}{ 7x } }{ x^2-8x }=\frac{ \color{purple}{ 9x-16 } }{ x^2-8x } \end{aligned} $$