All these people saying that you don't need maths for commerce yet also saying you need maths for commerce :|
I never said what degree and level of knowledge that is required (and not assuming he/she is doing general/2u/3u/4u). But yes you do need to know maths nonetheless cause it does help.
As we have said, you need to specify which particular areas you intend to study. B Arts is a generic degree and can incorporate many different units. At Macquarie you can do Economics, Mathematics, Statistics (which is required for many subjects), science and many others. Computing has maths.
I do analytical chemistry and we learn additional statistics and we are required to have knowledge in differentiation, calculations of log and many other mathematical components. Biochemistry has maths and quite a bit of calculations to determine dilution factors or concentrations.
Commerce and business itself has many various branches and pathways. Accounting, Finance, Actuarials, and economics. There are equations and numbers involved. Things like ratios and cash flow. Understanding on how to manage your own business and sales. Income, profit, expected interest, interest rates, debts and much more.
Maths is a universal language and you are expected to know the fundamentals but having a background in the area you make your life much more easier. I said commerce requires maths, and it does as everyone has stated.
And Natstar, unless Maths is taking up too much study time then dropping it will help. But, remember your UAI is only composed of your 10 best unit points so it doesnt have to count.