HELP WITH 9 AND 10! I really don’t understand how to find these!

50 and C

Step-by-step explanation:

Remark.

The geometric mean is the middle number between two numbers that are 2 places apart. It's easier just to make up an example to show what the mean is

4 8 16

8 is the geometric mean of 4 and 16. The first term (4) is multiplied by 2. The third term is derived from 8 (the mean) multiplied by 2

So to solve this problem you need to find what a is multiplied to get get the mean, and multiplied again by the same thing you did before to go from the mean to the third term.

Solution

12 / mean = mean / a      Cross multiply

mean^2 = 12*a

But the mean is given as 10sqrt(6)

12a = 100 * 6

12a = 600

a = 50

20 / mean = mean /a

mean^2 = 20 a

mean = 10 sqrt (10)

100 * 10 = 20*a

a = 1000 / 20

a = 50

here is your mark brainliest