"90 miles south and 20 miles east of port"
means the direction along which the ship must sail is:
x=-90, y=20
angle = atan(20,-90) = 180° - 12°-31'-44"
= 167°-28'-16" (in trigonometry notation).

To convert trigonometry notation to bearing, subtract angle from 90° or 450° if the angle exceeds 90°.

Bearing (clockwise from north)
= 450° - 167°-28'-46"
= 282°-31'-44"

A ship leaves port A and travels north for 47km and arrives at port B.It then travels east to port C which lies 35% of port A.How far is port C from port B? Draw a diagram to help you calculate.