Number 1 is simple arithmetic. Make the South latitude a negative number so:
15º54'30" - (-10º33'30")
Which, because the minus signs cancel each other, is the same as
15º54'30" + 10º33'30"
My answer:
26º28'00"
It may help to visualise it by drawing some lines on a bit of paper with the equator in the middle.
2. This is another simple one that has been intentionally made to look complicated by adding unnecessary information. Magnetic course is just the true course +/- any variation. You add west variation to get magnetic course and you subtract east variation ("variation east, magnetic least, variation west, magnetic best"). All the stuff about wind and airspeed is just there to confuse you.
Answer:
055ºT+006º=061ºM
3. Ground speed is just true air speed +/- wind component. Once again the question is trying to confuse you by adding unnecessary information. Headwind makes the ground speed slower than TAS and a tailwind makes the ground speed faster so:
80-20 = 60 knots ground speed.