PQR is an isosceles triangle in which PQ=PR M and N are points on PQ and PR such that angle MRQ=angle NQR

Prove that triangles QNR and RMQ are congruent

In the first triangle 80+20+p=180 (since sum of all angles of a triangle is 180)so p= 80also in second triangle 55+45+q=180 (since sum of all angles of a triangle is 180)so q=80so we can conclude that p=80 degrees q=80 degrees so p=q=80 degreeshence option b is correct