In ΔPQR,
$\angle PQR = \angle PRQ$
∴ PQ = PR ………………………(i)
Given,
$ \dfrac{QR}{QS} = \dfrac{QT}{PR}$ Using equation (i), we get
$\dfrac{QR}{QS} = \dfrac{QT}{QP}$……………….(ii)
In ΔPQS and ΔTQR, by equation (ii),
$\dfrac{QR}{QS} = \dfrac{QT}{QP}$
$\angle Q = \angle Q$
∴ ΔPQS ~ ΔTQR [By SAS similarity criterion]