The perimeter of a $\parallel$gm is $120\;cm$. If one side is greater than the other by $20\;cm$ . Find the length of the sides of the 11 gm

Question

$\begin{array}{1 1} 10\;cm,30\;cm \\ 15\;cm,35\;cm \\ 40\;cm,80\;cm \\ 20\;cm,40\;cm \end{array} $