I am assuming that parallelogram QRST is rectangle. RS is the width and ST is the length. RT is the diagonal. RU is half of the diagonal and TU is the other half of the diagonal.
Length = 12 ; Width = 10
to find the diagonal: d = √(L²+W² d = √ 12² + 100² d = √ 144 + 100 d = √244 d = 15.62
