Three forces with magnitudxes 100, 50 and 80 lbs act on an object at angles of 50 degree, 160 degree and -20 degree respectively.

Answer 1

I assume you want the resultant force? Just convert the polar coordinates to rectangular, add them, and convert back to polar:

(100,50°) = (64.28,76.60)
(50,160°) = (-46.98,17.10)
(80,-20°) = (75.18,-27.36)
add them to get
(92.48,66.34) = (113.81,35.65°)