Radio button or checkbox with fill-in blank

Is it possible to include a radio button or checkbox item that also includes a blank to be filled in by the user? For example, it might say "Yes, I want to donate. Amount: $_____." The blank would be for filling in by the user. In addition, I would want that value filled in to be used for later calculation.

Unfortunately, no that is not possible with a radio button or checkbox.

However, you can add a separate textbox where user can input the amount.

You can then set a condition where the amount field will only be shown once user selects Yes.

https://www.jotform.com/help/316-How-to-Show-or-Hide-Fields-Base-on-User-s-Answer

For calculations, please see this guide:

https://www.jotform.com/help/259-How-to-Perform-Form-Calculation-Using-a-Widget