If the List Box contains several linear equations separated by commas then clicking on the Solve by Substitution button opens this window. The equations appear at the bottom, left of the window. They are considered to be a system whose simultaneous solution is sought.
You can enter any number of equations and any number of unknowns. The coefficients must be numbers. For this example we entered:
2 x + 3 y = 4, 5 x + 6 y = 7
In the substitution method, the system of equations is solved by choosing one equation, setting it aside and solving it for one variable, and then substituting this into the remaining equations. In this program you do this by clicking on one of the variables in one of the equations. In this example we clicked on the variable x in the first equation (circled in red). This causes this equation to be grayed out in the remaining list and the solved-for version to be put on the set aside list. (It is grayed out because you can still change your mind and click on other variables.) Clicking on OK locks in your choice, and this equation is then substituted into the remaining equations.
The process is repeated until there are no equations left on the remaining list. Then the back-substitution phase is begins. When it ends, you can close the window. The entire dialog is copied into the Workspace.