If the average arithmetic mean of 8,12,15,21, X and 11 is 17 then what is X?

A.M = Arithmetic Mean
A.M = 17 Total Figures =06
A.M = (8+12+15+21+ X + 11) / 06
17 = (8+12+15 + 21+ X + 11) / 06
17 = (67 + X) / 6
17*6=67 + X
102 = 67 + X
102-67 = X
35 = X