The way I was taught, given a vague expression like that you evaluate by the normal rules as far as you can so 6/2(3) then you evaluate left to right :P. Alternatively, you could get one of those old HP calculators that do computation in prefix notation :D. Arithmetic using prefix notation completely eliminates any ambiguity about what should be done first. Infix notation (what you all know) is usually easier to read though, and I guess people saw ambiguity as an acceptable downside :P.
Prefix notation for both calculations:
* / 6 2 + 1 2
/ 6 * 2 + 1 2