Subtract $ \dfrac{4}{m} $ from $ \dfrac{5}{m} $ to get $ \dfrac{1}{m} $.

To subtract expressions with the same denominators, we subtract the numerators and write the result over the common denominator.

$$ \begin{aligned} \frac{5}{m} - \frac{4}{m} & = \frac{5}{\color{blue}{m}} - \frac{4}{\color{blue}{m}} =\frac{ 5 - 4 }{ \color{blue}{ m }} = \\[1ex] &= \frac{1}{m} \end{aligned} $$

Divide $ \dfrac{5}{4} $ by $ \dfrac{1}{m} $ to get $ \dfrac{ 5m }{ 4 } $.

Step 1: To divide rational expressions, multiply the first fraction by the reciprocal of the second fraction.

Step 2: Multiply numerators and denominators.

Step 3: Simplify numerator and denominator.

$$ \begin{aligned} \frac{ \frac{5}{4} }{ \frac{\color{blue}{1}}{\color{blue}{m}} } & \xlongequal{\text{Step 1}} \frac{5}{4} \cdot \frac{\color{blue}{m}}{\color{blue}{1}} = \\[1ex] & \xlongequal{\text{Step 2}} \frac{ 5 \cdot m }{ 4 \cdot 1 } \xlongequal{\text{Step 3}} \frac{ 5m }{ 4 } \end{aligned} $$