I need help.

solve for k.
881 = k - (-243)
k=?

Simplify the expression. -2/5(10+15m-20n)

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%

80 points suppose marcy made 45 posts online. if 23 of them contained an image, what percent of her posts had images? round your answer to the nearest whole percent. 54 percent 51 percent 49 percent 48 percent