$\mathrm{S}$ and $\mathrm{T}$ are points on sides $\mathrm{PR}$ and $\mathrm{QR}$ of $\triangle \mathrm{PQR}$ such that $\angle \mathrm{P}=\angle \mathrm{RTS}$.

Solution:

In figure, We have RPQ and RTS in which

$\angle \mathrm{RPQ}=\angle \mathrm{RTS}$ (Given)

$\angle \mathrm{PRQ}=\angle \mathrm{SRT}(\mathrm{Each}=\angle \mathrm{R})$



Then by AA similarity criterion, we have

$\Delta \mathrm{RPQ} \sim \Delta \mathrm{RTS}$