${W_t} = \frac{1}{2}k{x^2} = \frac{1}{2}k{\left( {\frac{A}{2}} \right)^2} = \frac{1}{4}k\frac{{{A^2}}}{2} = \frac{1}{4}W$

${{\rm{W}}_{{\rm{d\;}}}} = {\rm{W}} - {{\rm{W}}_{\rm{t}}} = {\rm{W}} - \frac{1}{4}{\rm{\;W}} = \frac{3}{4}{\rm{\;W}} \Rightarrow \frac{{{{\rm{W}}_{\rm{d}}}}}{{{{\rm{W}}_{\rm{t}}}}} = 3$.