Use the distributive property.

Combine like terms

Multiply $ \dfrac{4}{5} $ by $ n $ to get $ \dfrac{ 4n }{ 5 } $.

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

Step 2: Multiply numerators and denominators.

Step 3: Simplify numerator and denominator.

$$ \begin{aligned} \frac{4}{5} \cdot n & \xlongequal{\text{Step 1}} \frac{4}{5} \cdot \frac{n}{\color{red}{1}} \xlongequal{\text{Step 2}} \frac{ 4 \cdot n }{ 5 \cdot 1 } \xlongequal{\text{Step 3}} \frac{ 4n }{ 5 } \end{aligned} $$

Subtract $5$ from $ \dfrac{4n}{5} $ to get $ \dfrac{ \color{purple}{ 4n-25 } }{ 5 }$.

Step 1: Write $ 5 $ 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 $\color{blue}{5}$.

$$ \begin{aligned} \frac{4n}{5} -5 & \xlongequal{\text{Step 1}} \frac{4n}{5} - \frac{5}{\color{red}{1}} = \frac{ 4n }{ 5 } - \frac{ 5 \cdot \color{blue}{ 5 }}{ 1 \cdot \color{blue}{ 5 }} = \\[1ex] & \xlongequal{\text{Step 2}} \frac{ \color{purple}{ 4n } }{ 5 } - \frac{ \color{purple}{ 25 } }{ 5 }=\frac{ \color{purple}{ 4n-25 } }{ 5 } \end{aligned} $$