I was happily distracted this morning by this lovely problem, Create a System of Two Equations by Daniel Luevanos on Open Middle, accessible for students yet such a great task for mathematical thinking. We could discuss inequalities here as well as simultaneous equations.
Noting the link to a Desmos page as a suggested answer I couldn’t resist creating a more general Desmos page.
Now we could systematically change one variable at a time and start talking about inequalities….
Note you can search by grade using the drop-down menus and you will find a clear index on the right hand side of the home page.