adding a variable to a static text box

I need to add a variable to a static text box- can anyone help? The data entry text box comes with a variable, but how do you add a variable to a static text box?

The static text box contains a "model answer" that appears after a student enters their response to a question. I have a javascript that allows students to print out their response (this is simple because the student response section has a variable- it's a data entry text box) but I'd like them to also print out the model answer, which is static text. My javascript needs a variable to work, so I'm trying to figure out how to add a variable to the model answer text.

Any advice would be much appreciated.