Let A be the beginning point. After 85.5 m, it comes to point B.
Then it makes a 150° angle (180° - 30° = 150°) and procedes 45.0 m to point C.
You wish to find the distance from point A to point C.
Side AB = c, side BC = a, and side AC = b.
Use the Law of Cosines: b2 = a2 + c2 - 2a·b·cos(B)
---> b2 = 45.02 + 85.52 - 2· 45.0 · 85.5 · cos(150)
Can you finish this?