The ratio of time spend for stretching to time spend for exercise remain same.
Equate the ratio of time spend for stretching to time spend for exercise in both cases.
[tex]\begin{gathered} \frac{2}{15}=\frac{15}{x} \\ x=\frac{15\cdot15}{2} \\ =112.5 \end{gathered}[/tex]So Ruby spend 112 and a half minute to spend 15 minutes in stretching.
So answer is 112.5 min or
[tex]112\frac{1}{2}[/tex]