Multiplying wrong

I have two text boxes in which students can put amounts and hit a calculate button for the result.  I am using the expression function with each box as a variable.  The problem is the answer generated is wrong.  It is not always off, but for the answer I need the student to get the answer is wrong.  I have a work around by adding the missing amount if the answer generated is the amount captivate keeps generating.  However, I would love to know what is really wrong.  I tried recreating the slide thinking this was just a Captivate Gremlin, but no luck.

Any help would be great.