X^2/3-5X^1/3+6=0 i need help

X^2/3-5X^1/3+6=0
let u = X^1/3

u^2 - 5u + 6 =0
(u -2) (u-3) =0
u=2 or u=3
X^1/3 = 2
x = 8
answer
X^1/3 = 3
x = 27
answer