Can someone help with this please?

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%

Rounded to the nearest tenth, what is the value of x

If f(x) = 3x-2 and g(x) =2x+1 find (f-g)(x)