Multiply $itw$ by $ \dfrac{x}{o} $ to get $ \dfrac{ itwx }{ o } $.

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

Step 2: Multiply numerators and denominators.

Step 3: Simplify numerator and denominator.

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

Add $-ipw$ and $ \dfrac{itwx}{o} $ to get $ \dfrac{ \color{purple}{ -iopw+itwx } }{ o }$.

Step 1: Write $ -ipw $ 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 $\color{blue}{ o }$.

$$ \begin{aligned} -ipw+ \frac{itwx}{o} & \xlongequal{\text{Step 1}} \frac{-ipw}{\color{red}{1}} + \frac{itwx}{o} = \frac{ \left( -ipw \right) \cdot \color{blue}{ o }}{ 1 \cdot \color{blue}{ o }} + \frac{ itwx }{ o } = \\[1ex] & \xlongequal{\text{Step 2}} \frac{ \color{purple}{ -iopw } }{ o } + \frac{ \color{purple}{ itwx } }{ o }=\frac{ \color{purple}{ -iopw+itwx } }{ o } \end{aligned} $$

Multiply $ \dfrac{-iopw+itwx}{o} $ by $ \dfrac{f}{fiwy+1} $ to get $ \dfrac{ -fiopw+fitwx }{ fiowy+o } $.

Step 1: Multiply numerators and denominators.

Step 2: Simplify numerator and denominator.

$$ \begin{aligned} \frac{-iopw+itwx}{o} \cdot \frac{f}{fiwy+1} & \xlongequal{\text{Step 1}} \frac{ \left( -iopw+itwx \right) \cdot f }{ o \cdot \left( fiwy+1 \right) } = \\[1ex] & \xlongequal{\text{Step 2}} \frac{ -fiopw+fitwx }{ fiowy+o } \end{aligned} $$