Take a look at what's actually in the columns. Is it a formula or is it a field? Is the fraction a decimal or a real fraction?
If it's a decimal, you can just add the two columns together in a formula or you can follow the instructions below.
If it's a fraction, probably the easiest way to do this is to put a text box on the report where you want the combined column to appear. Drag the numeric field/formula into the text box. Then drag the fraction into the text box, making sure to place it after the number. When dragging, you'll hover over the text box until it "activates" before dropping the field into it.
-Dell