You don't have to do any algebra. It's just division, multiplication, adding, subtracting, percentages etc. Some questions involve multiple calculations to get the answer their looking for. Also there were some speed, distance and time calculations.
You will be asked to give other examples in addition to the ones you wrote on your question paper. Its quite a relaxed interview, they want to get to know you as best they can so want you to elaborate on your skills and talents and give 'evidence' of when you used them. In my interview they went over the answers I provided, which was good because you have the opportunity to ensure they understand your desire to become a pilot. They must get so many very similar answers to the "when did you decide you wanted to be a pilot?" question, so its important to try and get a personal touch to ensure they believe you!
As far as I am aware stage 1 is passed once they look over your details you provide online, to check you meet the minimum requirements....but I may be wrong.
Nev.