A boy works 50m on a bearing 025 and then 200m due east. How far is he from his starting point
How can you "work 50 m" ??
anyway, make a sketch and you should be able to see that ...
using the cosine law:
distance^2 = 50^2 + 200^2 - 2(50)(200)cos 115°
evaluated the right side, noting that cos115 will be negative,
then take the square root to get "distance"