text: how do you subtract in excel.?   for example, if you have 100 in cell a1 and 37 in cell a3 and you want your answer in cell b10, type the following formula in cell b10: =a1-a3  make sure your formula does not have an apostrophe (') before the equal sign.  in other words, you don't want this: '=a1-a3  the apostrophe tells it you want text and the equal sign tells it you want a formula.