If the mean if these numbers is 9 what is x?

16,3, x, 5

The mean is the average number meaning that it is all the numbers in a set added together and divided by how many number are in the set. In this case there are 4 numbers (16, 3, whatever number x is, and 5). So, to find out what x is, first you multiple 4 by the known mean which is 9.

4 x 9 = 36

Then you simply subtract 36 from all the known numbers to find x.

36 - 16 - 5 - 3 = 12

So x = 12