Click Equations
on the Tools toolbar.Click Tools, Equations.
Allows you to edit all the equations, in a list format.
To edit equations:
Do one of the following:
Click Equations
on the Tools toolbar.
Click Tools, Equations.
Right-click the Equations folder 
in the FeatureManager design tree, and select Edit
Equation.
In the Equations dialog box, click Edit All.
In the Edit Equations dialog box, edit the text of one or more equations as needed. When editing, keep the following in mind:
Each equation must be on a separate line.
Dimension names must be enclosed in quotes.
Equations are solved left to right (that is, the dimension on the left is driven by the value on the right).
Equations are solved in the order in which they appear in the equation list. You can cut and paste equations to change the order, if necessary.
You can add comments to equations, to document your design intent.
If you make a mistake, click
Undo to clear each consecutive
value. You can clear one value each time you click Undo.
Click OK to close the Edit Equations dialog box.
The revised equation is displayed in the Equations dialog box.
Click OK
to close the Equations dialog
box, then click Rebuild 
on the Standard toolbar.