Algebra spent the whole period practicing solving systems by substitution. There are so many different techniques for solving with substitution (solving both equations for a variable, solving only one, distributing, factoring out a common multiple, ect) so we will be spending quite a bit of time here.
Their opener was this:
The sum of two numbers is 161. Their difference is 35. What are they?
They have had four or five of these so I finally introduced the system of equations method to solving these sorta question. It might have been too soon (Elimination is probably the easiest way to do this). We will come back to them after a bit of practice and hopefully thing will be cleared out.
Systems of equations seem to be a pretty big talking point in the math blogosphere. Let me know if you have come across any great resources on these!