Student Work: Linear Equations

We’ve spent the last few days working with linear equations. Gave an exit ticket today with this question on it, and was fascinated by these two students’ responses.

Screen Shot 2014-10-21 at 7.17.05 PM
Screen Shot 2014-10-21 at 7.16.53 PM

The first student graphs the situation correctly, but gets the second question wrong — although the answer is simple arithmetic, and is also pretty easy to see from the graph.
The second student’s graph is incorrect, for what I think is an interesting reason (look closely!), yet he answers the second question correctly, contradicting the evidence from his graph.

How would you respond to these students’ work?

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