Question

See question 5 in the linked attachment

Answer 1

in trinagle rpq and rts

angle RTS = angle RPQ ( given)

angle TRS = angle PRQ ( common angle)

NOW as 2 angles of 2 triangles are equal that means 3rd angle is also equal.

lets prove this

in triangle RTS

RST+ RTS + TRS = 180

in triangle PRQ

PQR+ RPQ+ PRQ = 180

SO

RST+ RTS + TRS = PQR+ RPQ+ PRQ

We proved above that

RTS = RPQ AND TRS = PRQ

SO

angle RST = Angle PQR