The y intercept is anywhere the line crosses the y-axis. For example on the first graph it hits 1 on the y-axis. To find the slope you use rise/run (what I call it) so find two points and find the distance in between. For the bottom left graph you'd use the point (-1,0) and (0,2). Go to the up two from (-1,0) and to the right one to (0,2) which is 2/1. So your slope is 2 (aka b). I hope that helped!
