Probably best to insert an Equation Editor object. I don't know if you can
get at this directly from Visio or if you need to build one in, say, Word,
and copy it over.
There's always the slash "/" alternative, or you could build a shape that
has a horizontal line in it, and simply hit return to put text above and
below the line.
If you don't mind messing in the ShapeSheet, you could try the following to
make such a shape.
1. Draw a Rectangle
2. Draw a line in the middle of the rectangle
3. Select both shapes
4. Choose Shape > Operations > Combine
5. Window > Show ShapeSheet
6. Find the Miscellaneous.LockCalcWH cell and set the value to 1
7. Find the Geometry section that defines the square. It will have five
rows.
8 . Put your cursor somewhere in the section, then right-click and choose
Delete Section
You now have a shape that has a horizontal line in the middle, yet has nice
resizing handles. You can type text in this shape, placing a Return between
the lines to get nominator and denominators.
A little complex, but works nicely.
