is it 1d4=x and 1d12=y. Then x * y = table # and result??
No what ends up being the process is that you add the result of what you do to the d4 to the result of a d12 roll. As an example let's say you roll a 4 on the d4 and a 7 on the d12 you subtract 1 from the d4 result, getting you 3. You multiply the 3 by 12 to get 36 and then you add 36 to the result of the d12 making it so you add 7 + 36= 43.