I’m not exactly sure what your question is, but the equations mean this:
The slope intercept formula (y=mx+b) for both lines is above the graph. For the blue line, it’s y=2x the line starts at zero, because of the absence of a y intercept, or b, and goes up two for every one move to the right on the X axis. The red line is y=x, or to put it in simple terms, y=1/1x+0.
y is what you are solving for.
1/1x is how much you go up and how much you go right (one up, one right).
+0 is where you start on the y axis (in this case, zero.
I hope this cleared up any questions you have about this coordinate plane!