We know that QP and TR are parallel. We also know that ST is 30 units (QT + SQ = 24 units + 6 units = 30 units). We also know that PerimiterSQP = 20 units. Therefore, we can conclude that SQ/ST = PerimiterSQP/PerimiterSTR.
Plugging in values, we have:
6/30 = 20/PerimiterSTR => PerimiterSTR = 100 units