Add $17$ and $ \dfrac{x}{x} $ to get $ \dfrac{ \color{purple}{ 18x } }{ x }$.

Step 1: Write $ 17 $ as a fraction by putting $ \color{red}{ 1 } $ in the denominator.

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

$$ \begin{aligned} 17+ \frac{x}{x} & \xlongequal{\text{Step 1}} \frac{17}{\color{red}{1}} + \frac{x}{x} = \frac{ 17 \cdot \color{blue}{ x }}{ 1 \cdot \color{blue}{ x }} + \frac{ x }{ x } = \\[1ex] & \xlongequal{\text{Step 2}} \frac{ \color{purple}{ 17x } }{ x } + \frac{ \color{purple}{ x } }{ x }=\frac{ \color{purple}{ 18x } }{ x } \end{aligned} $$

Add $ \dfrac{18x}{x} $ and $ 2 $ to get $ \dfrac{ \color{purple}{ 20x } }{ x }$.

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

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

$$ \begin{aligned} \frac{18x}{x} +2 & \xlongequal{\text{Step 1}} \frac{18x}{x} + \frac{2}{\color{red}{1}} = \frac{ 18x }{ x } + \frac{ 2 \cdot \color{blue}{ x }}{ 1 \cdot \color{blue}{ x }} = \\[1ex] & \xlongequal{\text{Step 2}} \frac{ \color{purple}{ 18x } }{ x } + \frac{ \color{purple}{ 2x } }{ x }=\frac{ \color{purple}{ 20x } }{ x } \end{aligned} $$