Add $ \dfrac{x-5}{5} $ and $ \dfrac{2x-1}{2} $ to get $ \dfrac{ \color{purple}{ 12x-15 } }{ 10 }$.

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}{ 2 }$ and the second by $\color{blue}{ 5 }$.

$$ \begin{aligned} \frac{x-5}{5} + \frac{2x-1}{2} & = \frac{ \left( x-5 \right) \cdot \color{blue}{ 2 }}{ 5 \cdot \color{blue}{ 2 }} + \frac{ \left( 2x-1 \right) \cdot \color{blue}{ 5 }}{ 2 \cdot \color{blue}{ 5 }} = \\[1ex] &=\frac{ \color{purple}{ 2x-10 } }{ 10 } + \frac{ \color{purple}{ 10x-5 } }{ 10 }=\frac{ \color{purple}{ 12x-15 } }{ 10 } \end{aligned} $$