OMG IT WORKED MY NUMBER IS 108 HOW!?

The final step says "subtract it from your original number" instead of "subtract your original number." As an example, I chose 4, added 102 to get 106. Then I added 56 to get 162. I subtracted 47 to get 115. Then subtracted 115 from my original number (4) like step 5 told me, to get 4-115=(-111). But the answer it gave me is 111 because step 5 should say "subtract your original number." So maybe you should go back to school instead of telling others they're doing it wrong. Anyway, change the instruction for step 5 and you get 4 stars from me. As-is, only 3 stars.

Holy crap, I tried it and it worked... Twice.

This is a simple trick.

Imagine you pick some number: #.
Then you are asked to add a number A to it.
Then you are asked to add a number B to it.
Then you are asked to subtract a number C from it.
Finally, you are asked to subtract the original number (#).

The total final number you get is as follows:
Total = # + A + B - C - # = A + B - C

This "game" randomly generates the numbers A, B, and C each time it runs. Then it combines these numbers and spits out the result.

I wouldn't really call this a game. It is just a very simple math trick.

Ok, I'm impressed. How'd you do it?