I've learned a surprising amount of stuff from my years of gaming. Among them is that math is slow, even when it uses small numbers. I have played many a game with many different people, most of them intelligent and well educated. For whatever reason, as soon as math came into the game, things slowed to a crawl. I remember playing a D&D game once with an old college buddy. Every time it game to his turn, we'd have to wait while he compiled his bonuses, then added the dice together, a process that took minutes. "12 + 7 is..." Mind you, this man is a software engineer, and a good one, but small number arithmetic totally killed his momentum.
That sort of thing is absolutely unacceptable in this game. This game needs to be fast fast fast. So, no math in the die mechanics. Maybe you'll have to do some adding when pulling dice together to form a pool, but outside of that, no math. That means that successes need to be on a per die basis, not something you reach for by adding multiple dice together.
In the name of simplicity, I'm going to say that targets run from 1 - 5, and you need to beat that number on a d6 for it to be a success. In short, the target tells you what dice fail. Roll your pool, look for the target number and lower, strip them out, and count what's left. The more dice you've got after that, the better you did.
Now there's a mechanic with about as little math as I can imagine.