DS is taking a voluntary exam next week to secure a place on a PhD in History in America. It's all good, his University results are excellent, he knows what he's doing BUT......... (always with the 'but' 
) there is a Maths section and he was so crap at Maths all through school that it took us a very great deal of money and tutor time to get him to A Level C to secure University course (also History!). The standard is US High School and includes Arithmetic, Algebra, Geometry and Data Analysis.
Does anyone, by any wild chance, know of a book/website where he can at least attempt to get an idea of what to try to get a grip on - and how to get that grip?
I will be forever in your debt for any ideas!