Combine like terms:

$$ \color{blue}{2x} + \color{blue}{2x} = \color{blue}{4x} $$

Multiply $ \dfrac{15}{x} $ by $ 2 $ to get $ \dfrac{ 30 }{ x } $.

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

Step 2: Multiply numerators and denominators.

Step 3: Simplify numerator and denominator.

$$ \begin{aligned} \frac{15}{x} \cdot 2 & \xlongequal{\text{Step 1}} \frac{15}{x} \cdot \frac{2}{\color{red}{1}} \xlongequal{\text{Step 2}} \frac{ 15 \cdot 2 }{ x \cdot 1 } = \\[1ex] & \xlongequal{\text{Step 3}} \frac{ 30 }{ x } \end{aligned} $$

Subtract $ \dfrac{30}{x} $ from $ 4x $ to get $ \dfrac{ \color{purple}{ 4x^2-30 } }{ x }$.

Step 1: Write $ 4x $ 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 $\color{blue}{ x }$.

$$ \begin{aligned} 4x- \frac{30}{x} & \xlongequal{\text{Step 1}} \frac{4x}{\color{red}{1}} - \frac{30}{x} = \frac{ 4x \cdot \color{blue}{ x }}{ 1 \cdot \color{blue}{ x }} - \frac{ 30 }{ x } = \\[1ex] & \xlongequal{\text{Step 2}} \frac{ \color{purple}{ 4x^2 } }{ x } - \frac{ \color{purple}{ 30 } }{ x }=\frac{ \color{purple}{ 4x^2-30 } }{ x } \end{aligned} $$

Add $ \dfrac{4x^2-30}{x} $ and $ 15x $ to get $ \dfrac{ \color{purple}{ 19x^2-30 } }{ x }$.

Step 1: Write $ 15x $ 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 $\color{blue}{x}$.

$$ \begin{aligned} \frac{4x^2-30}{x} +15x & \xlongequal{\text{Step 1}} \frac{4x^2-30}{x} + \frac{15x}{\color{red}{1}} = \frac{ 4x^2-30 }{ x } + \frac{ 15x \cdot \color{blue}{ x }}{ 1 \cdot \color{blue}{ x }} = \\[1ex] & \xlongequal{\text{Step 2}} \frac{ \color{purple}{ 4x^2-30 } }{ x } + \frac{ \color{purple}{ 15x^2 } }{ x }=\frac{ \color{purple}{ 19x^2-30 } }{ x } \end{aligned} $$

Add $ \dfrac{19x^2-30}{x} $ and $ 50 $ to get $ \dfrac{ \color{purple}{ 19x^2+50x-30 } }{ x }$.

Step 1: Write $ 50 $ 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 $\color{blue}{x}$.

$$ \begin{aligned} \frac{19x^2-30}{x} +50 & \xlongequal{\text{Step 1}} \frac{19x^2-30}{x} + \frac{50}{\color{red}{1}} = \frac{ 19x^2-30 }{ x } + \frac{ 50 \cdot \color{blue}{ x }}{ 1 \cdot \color{blue}{ x }} = \\[1ex] & \xlongequal{\text{Step 2}} \frac{ \color{purple}{ 19x^2-30 } }{ x } + \frac{ \color{purple}{ 50x } }{ x }=\frac{ \color{purple}{ 19x^2+50x-30 } }{ x } \end{aligned} $$