a.
1) find the value of the missing angles.
We know that within a triangle, it’s three angles combined always equal 180. There are two triangles visible, so we can find the missing angles, specifically R.
angle of R= 180 - 42 - 28 = 110
2) because you now know all angles of the triangle, you can use sine law to find a side.
r/sinR= q/sinQ
q = [r(sinQ)]/[sinR]
= [380(sin(42))]/[sin(110)]
q = 270.588...
3) Use sin law again to find side length of y
y = [270.588...(sin(28))]/[sin(90]
= 127.033...
y = 127 m
b.
we actually found this side length already
PR = 270.588...
PR = 271 m