A students 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?
Choose the most appropriate option:	A) 3	B) 7	C) 17	D) 31	E) 10
Solution   Clearly, we have (3+11+7+9+15+13+8+19+17+21+14+x/12)	=12   Number in place of x is   137+x=144   x= 144-137= 
<gadget id="calculator">144-137</gadget>
<output>7</output>
7.   Answer 7
<result>B</result>
A students 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?