The first answer is the departure formula , a quick look shows that it puts you down on the equator where as you travel east and then back up the meridian you wouldnt use departure (ch long x cos lat) BUT as you come back west you would then use the departure formula and so you will not end up where you started due to the earths spherical shape (hence using departure)
The second question i remember ( and had on my exam in March) but cant recall the answer , Bristol do have the full explaination on the databank tho , it just involves you drawing it out , the other 3 answers are obviously wrong when you draw it.
Hope this isnt too garbled im having 2 mins from Met and Instruments but both explanations are on the DB
DW