$$\begin{gathered} \mathrm{w}/\mathrm{v} \mathrm{strength} = \frac{17}{56}\times \mathrm{Volume} \mathrm{strength} \\ 3= \frac{17}{56}\times \mathrm{Volume} \mathrm{strength} \\ \mathrm{Volume} \mathrm{strength} =9.88 \\ 1 \mathrm{ml} {\mathrm{H}}_2{\mathrm{O}}_2 \mathrm{produces} =9.88\mathrm{ml} \mathrm{O}2 \\ 150\mathrm{ml} \mathrm{of} {\mathrm{O}}_2 \mathrm{produced} \mathrm{by} = \frac{1}{9.88}\times 150 =15\mathrm{ml} \end{gathered}$$