Jack walks at a pace of $5$ kilometres per hour. We calculate the distance Jack has walked with the formula $\orange{s} = 5 \cdot \blue{t}$.
Here, the $\orange{\text{distance}}$ is denoted in kilometres with the variable $\orange{s}$, and the $\blue{\text{time}}$ is denoted in hours with the variable $\blue{t}$. Using this formula, we can calculate the distance $\orange{s}$ for different values of time $\blue{t}$.

If Jack walks for $\blue{2}$ hours, $\blue{t}=\blue{2}$.
We get $\orange{s}= 5 \cdot \blue{2} = \orange{10}$, so Jack has walked $\orange{10}$ kilometers.
If Jack walks for $\blue{4}$ hours, $\blue{t}=\blue{4}$.
We get $\orange{s}= 5 \cdot \blue{4} = \orange{20}$, so Jack has walked $\orange{20}$ kilometers.

The formula:

$$\orange{s} = 5 \cdot \blue{t}$$

If $\blue t=\blue 2$, then $\orange{s}= 5 \cdot \blue{2} = \orange{10}$

If $\blue t=\blue 4$, then $\orange{s}= 5 \cdot \blue{4} = \orange{20}$