The mean of six numbers is 15. If 2 is taken away from every number, the new mean would be:

13 4 17 8

13

Sum of 6 numbers = 15 x 6 = 90 If 2 is taken away from every number, then, the sum equals to 90 - 12 = 78 Thus, mean = \(\frac{ 78}{6 }\) = 13