在Rails 3的文本字段中不能显示小数吗

I have a brief question... pretty new to rails, and I was wondering if you could help me with an issue that I'm having in code. I have a set of input boxes (it's an online app that asks for revenues and expenses) where I would like to format the currency. I've been using the following line of code for other independent input boxes (text_fields) within the app, but for some reason, it wont work when i try to add it to the income statement fieldsI have a brief question... pretty new to rails,