If I want to calculate mod(5a,3a), I would like the answer '2a', as 5a = 3a * 1 + 2a.
However, when I calculate
Mod[5 a, 3 a]
the result returned is
(5 a) mod (3 a)
which, although accurate, is not what I want.
As you might guess, I am VERY new with Mathematica...