isn't that middle term a mean?

im try:

2x, 3x, 8x

let x be the unknown number

consider m be the mean then 2x/m = m/8x

m = sq. rt of 16x^2

m = 4x this is the mean or middle.

so, 4x + 4 = 3x

x = - 4 ...

this substitute...

hope this is ryt . correct me if i'm wrong.. thanks