So to find the mean you add them all together and divide by the number of numbers there is so 11+15+19+17+23+20+17+18+21=174 and there are 10 numbers so it would be 174/10 which is 17.4 so you answer is 17.4
A constant is a number that never changes value. Example:
x + 3 = 5, 3 and 5 are constants.
multiply 20 by 500. it should help you with the problem.
