TeX source:
\begin{array}{rclcr}80\,\% &\widehat{=}& 60\,\text{km} \cr \cr 1\,\% &\widehat{=}& \dfrac{60\,\text{km}}{80} \cr \cr 100\,\% &\widehat{=}& \dfrac{100\cdot 60\,\text{km}}{80} &=& 75\,\text{km} \end{array}