$$ 8 \cdot -5 = -40 $$

Add $-40$ and $ \dfrac{-1}{4} $ to get $ \dfrac{ \color{purple}{ -161 } }{ 4 }$.

Step 1: Write $ -40 $ as a fraction by putting $ \color{red}{ 1 } $ in the denominator.

Step 2: To add fractions they must have the same denominator.
We can create a common denominator by multiplying the first fraction by $\color{blue}{ 4 }$.

$$ \begin{aligned} -40+ \frac{-1}{4} & \xlongequal{\text{Step 1}} \frac{-40}{\color{red}{1}} + \frac{-1}{4} = \frac{ \left( -40 \right) \cdot \color{blue}{ 4 }}{ 1 \cdot \color{blue}{ 4 }} + \frac{ -1 }{ 4 } = \\[1ex] & \xlongequal{\text{Step 2}} \frac{ \color{purple}{ -160 } }{ 4 } + \frac{ \color{purple}{ -1 } }{ 4 }=\frac{ \color{purple}{ -161 } }{ 4 } \end{aligned} $$