21 out of 25 question right what’s the grade

What is the value of x? enter your answer in the box. photo attached.

Which expression is equivalent to 8(k + m) − 15(2k + 5m)?

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%