What is the additive inverse of one half

The weight of a small starbucks coffee is a normally distributed random variable with a mean of 340 grams and a standard deviation of 11 grams. find the weight that corresponds to each event. (use excel or appendix c to calculate the z-value. round your final answers to 2 decimal places.)highest 30 percent middle 70 percent highest 90 percent lowest 20 percent