I once attended a airline selection, which required long division, which was out of vogue when I was at school, luckily my older brother who did long division at school, gave me a tutorial. I wouldn't get to worried about maths, but often what is lack in pilots is sines and cosines. Example as follows:
You are going to land on runway 27, the wind is 240 degrees at 20kts,
Q. What is the crosswind and headwing conponent without using a calculator or tables:
A. Headwind is 17.2 degrees and crowind is 10 degress.
How would you know that? difference between runway heading and wind is 30 degrees. You should know that Sin 30 = 0.5 and Cosine 30 = 0.86. Sin equals crosswind, so 0.5 equals, crosswind equals 0.5 x 20kts = 10kts, likewise Cosine equals headwind, so Cosine 30 equals 0.86, so 0.86 x 20 knots, which is a headwind of 17.2 kts.
Another thing to ask yourself, could your explain to an interview panel the trignometry behind the one in sixty rule?
Likewise know the ROD and heights rule of thumb for a specific glidescope of 3 degrees for a specific speed.
If you have GCSE in Mathematics I think that is good enough, but you need to demonstrate you can think on your feet.
As previous mentioned there is probably a lot of matter on the internet on this subject.