math
posted by Pamela .
A ship leaves POrt P and sails 28km away on bearing of 70 degrees to POrt Q. The ship then turns on a bearing of 160 degrees and sails 21km to POrt R. Find angle PQR, calculate the distance PR, Determine the bearing of R from P.
angle PQR = 180 degrees  160 degrees = 20 degrees

ships sail on headings, not bearings.
Angle PQR is not the angle between the NS line and R. It is the angle between PQ and QR. That is, 70 + 20 = 90 degrees.
So, now we can figure the xy displacements:
PQ = <28sin70°,28cos70°> = <26.31,9.58>
QR = <21sin20°,21cos20°> = <7.18,19.73>
Add them up and you get PR = <33.49,10.15> = 35.00 at 106.88° 
Dp yygg