\(\frac{2}{5} MR ^2 \omega_1=\frac{2}{5} M \left(\frac{ R }{4}\right)^2 \omega_2\)
\(\Rightarrow MR ^2 \omega_1=\frac{ MR ^2}{16} \omega_2\)
\(\Rightarrow \frac{\omega_1}{\omega_2}=\frac{1}{16} \Rightarrow \frac{ T _2}{ T _2}=\frac{1}{16} \Rightarrow \frac{ T _1}{ T _2}=\frac{16}{1}=\frac{ t _1}{ x }\)
\(\therefore t _1=24 \Rightarrow \frac{16}{1}=\frac{24}{ t _2} \Rightarrow x =16\)