Well, the y-intercept is represented by B. So b would be the dot crossing the y-axis in each graph (which you already circled). Next, the slope for top left is: -1.5, top right is: -1.7, bottom left is: 3, and bottom right is: 1.33. I got those by using this very helpful website named Desmos. Now, I’m order to write the equation for each graph is very simple, all you have to do is put in the slope and y-intercept into the equation. For example, the top left one would be:
y = -1.5x + 4 since we know that the slope is equal to -1.5 and the y-intercept is equal to 4. Hope this helps :)