Variable with exponential equation help

Hi there, I seem to be having trouble with this equation. (X^3+5)/4=8

My idea was to multiply the values inside the bracket by 4 to undo the division, and then to do the same to the RHS...ie. 4x8, and work from there...but this gave me x= 1.4422495

But this method does not work out. I used my casio Classpad 330 to solve the equation, and x=3

Can someone give me a heads up where I am going wrong(Speechless)

Re: Variable with exponential equation help

Re: Variable with exponential equation help