A boy walk 6km from a point P to a point Q on a bearing of 065. He then walk to a point R, a distance of 13km ,on a bearing of 146.(1) sketch the diagram of his movement. (2) find the distance of PR

After you made your sketch you will see that triangle PQR has angle Q = 99°, and

we can just use the cosine law:
PR^2 = 6^2 + 13^2 - 2(6)(13)cos99°
=36+169-(-24.403...)
= 229.403..
PR = √299.403.. = 15.146