prove that segment ls of parallelogram lens is parallel to segment gt of parallelogram gthn

Question

I a'm supposed to prove that segment ls of parallelogram lens is parallel to segment gt of parallelogram gthn in 4 steps given that lens and gthn are parallelograms. I don't quite know how.

Answer 1

If you drew lens with le parallel to gt, calculating the slope of gt and le showing that these slopes are equal, this proves that the sides are parallel.