SOLUTION: Twelve is the geometric mean of 9 and what number?

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Question 517006: Twelve is the geometric mean of 9 and what number?
Answer by JBarnum(2146) About Me  (Show Source):
You can put this solution on YOUR website!
12=%289%2Bx%29%2F2 multiply both sides by 2
24=9%2Bx subtract 9 from both sides
15=x
9 and highlight%2815%29 has mean of 12