For perpendicular questions, you need to find the reciprocal of the slope and change it's sign.
I sent a picture to show you what I mean
With your graph questions, remember
rYse over run
This is for your slope. for example, with number 19, go up 7 over the right 4(Because it's a positive number) starting from the y-intercept but also backtrack so it's a line and your y-intercept, b, the number after the slope is the point where the line meets the y- axis. So for number 19, you would plot a point at (0, -4)
I'm not entirely sure that's how the slope things go (The actual slope not the y-intercept) so I would suggest asking your teacher about that.
Sorry I couldn't help more! I just hope this makes you understand just a little bit more :)