sir i cannot grasp how you are getting the points to plot on the graph. yes i understand you sub in instead of x , you sub a number in and i understand the first one is always zero but after that im lost.
To graph a line you need to know any two points. If you have an equation of the line you use it to get get points. You do this by either subbing in an x value to get a corresponding y values; or sub in a y value to get the corresponding x value. You can sub in any number you wish. It is usually easiest to sub in 0 for x and get the point where the line crosses the y axis, and then 0 for y and find where it crosses the x axis.
Look at the video linked here:
Any khan academy links for these I'm still struggling after using the book and these videos?
The Khan Academy Videos in this area are poor quality. Try this video https://www.youtube.com/watch?v=BXWzNp-4ilA