Answer:
6sqrt(3)
20
sqrt(77)
Explanation:
x is the geometric mean of a and b if the following equation is true.
a/x = x/b
9 and 12
9/x = x/12
x^2 = 9 * 12
x^2 = 108
x = sqrt(108)
x = 6sqrt(3)
16 and 26
16/x = x/25
x^2 = 16 * 25
x^2 = 400
x = 20
7 and 11
7/x = x/11
x^2 = 7 * 11
x = sqrt(77)