You didn't include any expression in your post, but I think you should turn that question around and look at it from the PICAXE point of view.
For example: a = 2b+1 or a = (2 x b) + 1
How can PICAXE BASIC solve this expression?
Code:
symbol a = w0 ; limited to 0 to 65535, 16 bits
symbol b = w1 ; limited to 0 to 32767, due to equation, 16 bits
a = 2 * b
a = a + 1
It isn't very tedious in a real coded program, because you aren't constantly manipulating an equation. You develop and code a routine once.