Given:
According to isosceles triangle DG=TD
let length of DG is x.
so TD is x .
perimeter a triangle is: DG+GT+TD
GT=240cm
so equation is:
[tex]\begin{gathered} DG+GT+TD=756 \\ x+240+x=756 \\ 2x=756-240 \\ 2x=516 \\ x=258 \end{gathered}[/tex]so the length is DG=258 cm.