I did some research, and the first thing I found was this:
The slope would be -1/2. You would divide the right side by 2 to get rid of the 2 on he left. That would make the intercept -1/2 also.
If this is true, you are correct.
I don't understand.Ask you teacher for an explanation, and remember, mistakes are opportunities to learn.
P.S.-I love your nail polish!