จากโจทย์จะได้ว่า

PS = QR = 2QM = 2MR

PQ = SR = 2SN = 2NR

โดย

PQ + QM = PQ + PS/2 = u -----> 2PQ + PS = 2u   ---------------(1)

PS + SN = PS + PQ/2 = v ----------------(2)

(1)-(2),   PQ = (4u-2v)/3