isn't that middle term a mean?
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 ...
hope this is ryt . correct me if i'm wrong.. thanks