I've added a ZIP file into Semester 2 Updated Resources Book with all the updated files for the Systems of Linear Equations Unit. 

I wanted to share this slide because I enjoyed both of the activities on it with my classes.  I had already taught solving a system graphically and used these two activities to introduce number of solutions.  The "What do you see?" actvity I did as a think-pair-share and it was amazing the number of things the class came up with (slope, equation of lines, y-intercepts, parallel, pairs of lines that have solutions and pairs that don't, etc.).  The race activity is very simple but I think it helped the students visualize and gave us a chance to get out of the classroom.  What I do is take the students outside or to an open area in the school and I get two students to go through each of the cases.  I ask the class to look for the moment when both racers are side by side.  Then we come back to the class and graph each scenario for our notes.

Another good activity is Dan Meyer's Shower vs. Bath.  I used this one to transition from solving graphically to algebraically and as practice for modelling a situation. 

Hope this helps.  Please feel free to reply and give feedback or to share any of your ideas!

Colin