What maths will help one complete most if not all of project Euler questions? Last I've attempted project Euler I could not understand the questions/vocabulary, etc., and could only complete a few questions. I've gone over set theory, and college algebra and looking through the questions again they are more comprehensible.
I'd assume knowledge of discrete maths will help most with project Euler questions?
One text I'd recommend highly, and it will give you a very solid foundation in Discrete Math, and more, is Graham, Knuth, and Patashnik's Concrete Mathematics: A Foundation for Computer Science.
From the description available at the link above: