Most universities will ask for a Maths A-level if you wanna undertake an economics undergraduate degree as not every school offers economics A-level. So one of your 3 choices should definitely be maths. Due to this your first year of uni usually covers A-level topics to get everyone on the same page. I would say if you have the choice of taking Alevel economics, it will definitely be more helpful (I studied A-level maths, economics and business) than business due to economic terms and concepts- it just means you can relax a bit more than your classmates too.