As Lightning Mate said pick up a flight computer and it's a lot easier than cosines and sines.
To work out W/V you need heading, track/course, TAS & GS - basic triangle of velocities stuff just asked in a more practical manner.
GS = 42 NM in 5 mins = 504 kts.
In this case as both heading and track were magnetic work in magnetic on the CRP-5 and get a magnetic wind of 170/70 then ADD the variation back in to get true W/V 186/70 so D.
If you have a mixture of true and magnetic I would always work in true.
Gross error check - wind blows from heading to track so W/V must have a southerly element in this case, rules out answer A to start with.