Subtract $ \dfrac{1}{2} $ from $ x $ to get $ \dfrac{ \color{purple}{ 2x-1 } }{ 2 }$.

Step 1: Write $ x $ 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 $\color{blue}{ 2 }$.

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

Multiply $28$ by $ \dfrac{2x-1}{2} $ to get $ \dfrac{ 56x-28 }{ 2 } $.

Step 1: Write $ 28 $ as a fraction by putting $ \color{red}{1} $ in the denominator.

Step 2: Multiply numerators and denominators.

Step 3: Simplify numerator and denominator.

$$ \begin{aligned} 28 \cdot \frac{2x-1}{2} & \xlongequal{\text{Step 1}} \frac{28}{\color{red}{1}} \cdot \frac{2x-1}{2} \xlongequal{\text{Step 2}} \frac{ 28 \cdot \left( 2x-1 \right) }{ 1 \cdot 2 } = \\[1ex] & \xlongequal{\text{Step 3}} \frac{ 56x-28 }{ 2 } \end{aligned} $$