Fundamental mathematic proofs.... I know this may seem a slightly odd question, but are there any website or pdf files, etc, floating around of proofs of the basic pricipals and "tricks" of maths? eg - adding, subtraction, multiplication, division, fractional sums and products, percentages, etc? I ask because I feel that these basic bits of maths are often over looked as we are simply told "this is how you do this" - are there any algebraic proofs for these? Thanks.