you need to graph them. It's rather hard to explain graphing, but I'll give it a shot. since we know one slope form is y=mx+b, and we have that form, it becomes more simple. So we have 3, which is the y-intercept. The y-intercept line is the line that goes up vertically. Plot a point on the three. So then, the equation, y=4x. SO say x is 1. Then, y would be 4.If x was two, y would be 8. Make sure to plot all of the points and draw a line through. Hope this helps!
