Subtract $ \dfrac{29}{5} $ from $ 10 $ to get $ \dfrac{ \color{purple}{ 21 } }{ 5 }$.

Step 1: Write $ 10 $ as a fraction by putting $ \color{red}{ 1 } $ in the denominator.

Step 2: To subtract fractions they must have the same denominator.
We can create a common denominator by multiplying the first fraction by $\color{blue}{ 5 }$.

$$ \begin{aligned} 10- \frac{29}{5} & \xlongequal{\text{Step 1}} \frac{10}{\color{red}{1}} - \frac{29}{5} = \frac{ 10 \cdot \color{blue}{ 5 }}{ 1 \cdot \color{blue}{ 5 }} - \frac{ 29 }{ 5 } = \\[1ex] & \xlongequal{\text{Step 2}} \frac{ \color{purple}{ 50 } }{ 5 } - \frac{ \color{purple}{ 29 } }{ 5 }=\frac{ \color{purple}{ 21 } }{ 5 } \end{aligned} $$