I'm pretty sure that you are supposed to solve for b. So, if you just plug in (0, 0) for (x, y) in y = mx + b, then you get:
[tex]0=0m+b[/tex]
The term with the m cancels out, because anything multiplied by 0 is just 0, and we are left with:
[tex]0=b[/tex]
So, that's how I'd solve it.
