The approach here is to decompose all directions into North and East and then do simple Cartesian addition of the obtained coordinates.
S1 = 399 E
S2 = 552 Km 58.5 deg west of north ;
= 552 cos (58.5) N - 552 sin (58.5) E
= 288.41 N - 470.65 E
S3 = 890 N
total S = (890 + 288.41) N + (399 - 470.65) E
S = 1178.41 N - 71.65 E
D =
![√(N^2 + E^2)](https://img.qammunity.org/2019/formulas/physics/high-school/i8480h52mbj68lwtaskbtpxgqq39440i8q.png)
D = 1180.58 Km
direction = atan(N/E) = -86.52 deg
means : 3.48 deg west of north