Answer:
C 62°
Explanation:
the triangles RST and PQT are both right-angled triangles.
and we know in both triangles and additional angle.
remember, the sum of all angles in any triangle is always 180°.
so, we know in both triangles the third angles too :
180 = 90 + 23 + angle PTQ
angle PTQ = 67°
180 = 90 + 39 + angle RST
angle RST = 51°
and remember also, that the sum of all angles around a single point on one side of a line is also 180° (because they represent a half-circle with the point being the center and the line being an extended diameter).
so,
angle PTQ + angle RST + angle RTV = 180
67 + 51 + angle RTV = 180
angle RTV = 62°