Answer:
18
Explanation:
since U is the midpoint of QT, QT = 2(QU)
similarly, QS = 2 (QR)
because QR is parallel to QS and QU is parallel to QT, triangle QUR is similar to triangle QTS. therefore, the scaling factor between QT/QU and QS/QR is equal to the scaling factor between RU and ST.
therefore,
ST = 2(RU)
36 = 2(RU)
18 =RU