Try using Goal Seek.
Enter 128.25 in cell A1
Enter 1 in cell B1
In C1 enter =B1^1.33
in D1 enter =A1*C1

B1 is where X is located. Launch Goal Seek. In Excel 2007 select Data ribbon
What-If Analysis Goal Seek. In earlier versions select Tools Goal
Seek.
Set it up like this:
Set cell: D1
To value: 0.28
By changing cell: B1

Click OK. It finds a solution that it determines is close enough. If it's
not close enough for you, copy A1:D1 down to row 2. In B2, enter something
like
=B1-0.00000001
Now copy A2:D2 down for about a thousand rows (make sure the value in column
A doesn't automatically increment). Somewhere around row 800 you will find
the closest match to exactly 0.28, unless you want to use more decimal places
(and lots more rows).

As you can see, the caret ^ is how you raise a number to a power in Excel.

Hope this helps,

Hutch

"Iriemon" wrote:

I am trying to solve the following equation for "X":

Sorry, Discussion group formatting will not allow me to write in superscript!
The last part is supposed to be "X" raised to the 1.33 power.

.28 = 128.25(X 1.33)

.28 = 128.25 times "X" raised to the 1.33 power

Must have forgot most of my algebra! :-(