How do you put -10(4x-5) into a equeation like 40x-50

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%

Prove that 16^4-2^13-4^5 is divisible by 11.

Which expression gives the exact value of x?