Multiplying 2 numbers that will automatically show the results

Hello. I'm new to Articulate and currently working with my Instructional Material right now. I just have a question.

Here's what I want to do:
1. Student will type in the answer (on Bromine chemical equation) since it has  a subscript of 2 it will automatically shown on the table of Bromine(reactants side) with the answer only and no button to show. See my screenshot for reference.

It's my first time to use this application and helped me produce my Instructional Material that I needed so I can graduate with my Master's Degree. Hope anyone can help.

Thanks all!