solve the system. y = 2 - 6x 12y - x = 1

Me because some of question i don’t understand

The first-serve percentage of a tennis player in a match is normally distributed with a standard deviation of 4.3%. if a sample of 15 random matches of the player is taken, the mean first-serve percentage is found to be 26.4%. what is the margin of error of the sample mean? a. 0.086% b. 0.533% c. 1.11% d. 2.22%

Your food costs are $5,500. your total food sales are $11,000. what percent of your food sales do the food costs represent?