If this is a one-off exercise, you can use 'Text to Columns'
Select cell A1, and from the Menu select Data - Text to Columns ...
then Next, check the 'Other' check box and enter x in the text box as a delimiter.
There are also formulas that can go in cells B1, C1 & D1 to extract the numbers. This is of use if the contents of cell A1 will change, but the structure (number x number x number) will not change.
Here is one set of formulas that you could use: