we know the 100% or total is 50 hours, and walking was only 10 hours.
[tex]\begin{array}{ccll} amount&\%\\ \cline{1-2} 50&100\\ 10&x \end{array}\implies \cfrac{50}{10}=\cfrac{100}{x}\implies 5=\cfrac{100}{x}\implies 5x=100 \\\\\\ x=\cfrac{100}{5}\implies x=20[/tex]
