Subtract $ \dfrac{10}{h} $ from $ 5h $ to get $ \dfrac{ \color{purple}{ 5h^2-10 } }{ h }$.

Step 1: Write $ 5h $ as a fraction by putting $ \color{red}{ 1 } $ in the denominator.

Step 2: To subtract raitonal expressions, both fractions must have the same denominator.
We can create a common denominator by multiplying the first fraction by $\color{blue}{ h }$.

$$ \begin{aligned} 5h- \frac{10}{h} & \xlongequal{\text{Step 1}} \frac{5h}{\color{red}{1}} - \frac{10}{h} = \frac{ 5h \cdot \color{blue}{ h }}{ 1 \cdot \color{blue}{ h }} - \frac{ 10 }{ h } = \\[1ex] & \xlongequal{\text{Step 2}} \frac{ \color{purple}{ 5h^2 } }{ h } - \frac{ \color{purple}{ 10 } }{ h }=\frac{ \color{purple}{ 5h^2-10 } }{ h } \end{aligned} $$

Subtract $2$ from $ \dfrac{5h^2-10}{h} $ to get $ \dfrac{ \color{purple}{ 5h^2-2h-10 } }{ h }$.

Step 1: Write $ 2 $ as a fraction by putting $ \color{red}{ 1 } $ in the denominator.

Step 2: To subtract raitonal expressions, both fractions must have the same denominator.
We can create a common denominator by multiplying the second fraction by $\color{blue}{h}$.

$$ \begin{aligned} \frac{5h^2-10}{h} -2 & \xlongequal{\text{Step 1}} \frac{5h^2-10}{h} - \frac{2}{\color{red}{1}} = \frac{ 5h^2-10 }{ h } - \frac{ 2 \cdot \color{blue}{ h }}{ 1 \cdot \color{blue}{ h }} = \\[1ex] & \xlongequal{\text{Step 2}} \frac{ \color{purple}{ 5h^2-10 } }{ h } - \frac{ \color{purple}{ 2h } }{ h }=\frac{ \color{purple}{ 5h^2-2h-10 } }{ h } \end{aligned} $$