Question: Math container help

I am a middle school teacher trying to program an app where a student will type in a linear equation in any form. They are to solve this for the variable Y and graph the line. I have most of this up and running, but I would like to include a step by step help system, where after entering the equation, the students can click on a button and it will display the 1st step to solve the equation. I am using the built-in function “LinearSolveSteps” in the Students [Basics] package. Every repeated click of the button would reveal the next step. I have this working to a point, but I don't seem to be able to add the next step into the math container without deleting the contents that are already in there. I have tried rebuilding the string by using the "+" but the + shows up in the equation and it is not on a new line. Any ideas would be appreciated. Thank you.