Use the distributive property.

Multiply $112$ by $ \dfrac{x^2}{7} $ to get $ \dfrac{ 112x^2 }{ 7 } $.

Step 1: Write $ 112 $ as a fraction by putting $ \color{red}{1} $ in the denominator.

Step 2: Multiply numerators and denominators.

Step 3: Simplify numerator and denominator.

$$ \begin{aligned} 112 \cdot \frac{x^2}{7} & \xlongequal{\text{Step 1}} \frac{112}{\color{red}{1}} \cdot \frac{x^2}{7} \xlongequal{\text{Step 2}} \frac{ 112 \cdot x^2 }{ 1 \cdot 7 } = \\[1ex] & \xlongequal{\text{Step 3}} \frac{ 112x^2 }{ 7 } \end{aligned} $$

Add $14$ and $ \dfrac{112x^2}{7} $ to get $ \dfrac{ \color{purple}{ 112x^2+98 } }{ 7 }$.

Step 1: Write $ 14 $ 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 $\color{blue}{ 7 }$.

$$ \begin{aligned} 14+ \frac{112x^2}{7} & \xlongequal{\text{Step 1}} \frac{14}{\color{red}{1}} + \frac{112x^2}{7} = \frac{ 14 \cdot \color{blue}{ 7 }}{ 1 \cdot \color{blue}{ 7 }} + \frac{ 112x^2 }{ 7 } = \\[1ex] & \xlongequal{\text{Step 2}} \frac{ \color{purple}{ 98 } }{ 7 } + \frac{ \color{purple}{ 112x^2 } }{ 7 }=\frac{ \color{purple}{ 112x^2+98 } }{ 7 } \end{aligned} $$

Multiply $ \dfrac{112x^2+98}{7} $ by $ x^3 $ to get $ \dfrac{ 112x^5+98x^3 }{ 7 } $.

Step 1: Write $ x^3 $ as a fraction by putting $ \color{red}{ 1 } $ in the denominator.

Step 2: Multiply numerators and denominators.

Step 3: Simplify numerator and denominator.

$$ \begin{aligned} \frac{112x^2+98}{7} \cdot x^3 & \xlongequal{\text{Step 1}} \frac{112x^2+98}{7} \cdot \frac{x^3}{\color{red}{1}} \xlongequal{\text{Step 2}} \frac{ \left( 112x^2+98 \right) \cdot x^3 }{ 7 \cdot 1 } = \\[1ex] & \xlongequal{\text{Step 3}} \frac{ 112x^5+98x^3 }{ 7 } \end{aligned} $$