Answer:
8 cm
Step-by-step explanation:
According to the condition,
[tex]\dfrac{PQ}{RS} = \dfrac{QT}{ST}\\\\\implies \dfrac{9}{3} = \dfrac{QT}{4}\\\\ \implies 3 =\dfrac{QT}{4}\\\\\implies QT = 3 \times 4 = 12~ \text{cm}\\\\\text{Hence}~ QS =QT - ST = 12 -4 = 8~ \text{cm}[/tex]
