The average (arithmetic mean) of 12, 25, and x is 21. what is the value of x? a. 24 b. 25 c. 26 d. 27 explain your answer.

The answer is 26, the average is found by adding all the numbers and dividing by how there are. you are given 2 sets (25,12) and need to find X, the average should be 21. 25+12 is 37, 37+(c) which is 26 = 63 , you then divide 63 by how many numbers you had , which is 3 and the answer is 21.

Cd is the perpendicular bisector of both xy and st, and cy=20.find xy