Here's one exactly like it step-by-step:

First put  in slope-intercept form:





 <--(when we find k, we'll substitute it here)







Compare that to y = mx+b and we see the slope m



This must equal to 



Cross-multiply:











Now we substitute that into the equation of the line:
Since that comes out a bad fraction (yours does too),
the easiest place to substitute it is in







Multiply through by 41







Divide through by -21



Now do yours exactly the same way.

Edwin