Answer :
Charles and his family walk at a steady speed of 1¼ mile per hour, so in hour, namely 60 minutes, they have covered 1¼ miles, how many minutes will it take them to cover 3/4 of a mile?
[tex]\bf \begin{array}{ccll} miles&minutes\\ \cline{1-2}\\ 1\frac{1}{4}&60\\\\ \frac{3}{4}&x \end{array}\implies \cfrac{~~1\frac{1}{4}~~}{\frac{3}{4}}=\cfrac{60}{x}\implies \cfrac{~~\frac{5}{4}~~}{\frac{3}{4}}=\cfrac{60}{x}\implies \cfrac{5}{4}\cdot \cfrac{4}{3}=\cfrac{60}{x} \\\\\\ \cfrac{5}{3}=\cfrac{60}{x}\implies 5x=180\implies x=\cfrac{180}{5}\implies x=36[/tex]