A student was asked to find the arithmetic mean of the numbers 3, 11, 7, 9, 15, 13, 8, 19, 17, 21, 14 and x. He found the mean to be 12. What should be the number in place of x ? Options.
A) 9
B) 7
C) 6
D) 1
E) 5
Explanation:   Clearly, we have (3 + 11 + 7 + 9 + 15 + 13 + 8 + 19 + 17 + 21 + 14 + x) / 12 = 12.   or 137 + x = 144 or x = 144 - 137= 
<gadget id="calculator">144 - 137</gadget>
<output>7</output>
7.   Answer: 7
<result>B</result>
A student was asked to find the arithmetic mean of the numbers 3, 11, 7, 9, 15, 13, 8, 19, 17, 21, 14 and x. He found the mean to be 12. What should be the number in place of x ?