War Pretzels - A game in which you NEED to have quick additiona nd subtraction skills. Use your NUMBER SENSE

Are you up to this addition and subtraction challenge? Welcome to the first annual all-pretzel arm wrestling tournament. Although you can't hope to match the pure strength of the world's best arm wrestling pretzels, you have one advantage - The strength of your pretzel-flexible arms is governed by your quick skills in addition and subtraction. Subdue your worthy opponents with your error-free calculations. Be careful though - errors you can afford to make in the first few rounds will lead to your demise in the last few rounds. Be quick ---- and accurate. The calculations get harder as you move on, but you'll have to make less of them in the later rounds.