I hope this helps. Since the slope of a horizontal line is 0 the general formula for the standard form equation y mx b becomes y 0x b y b. When the line is graphed m is the slope of the line and b is where the line crosses the y-axis or the y-intercept.
To write an equation in slope-intercept form given a graph of that equation pick two points on the line and use them to find the slope.
Try a smart search to find answers to similar questions. So the equation of any line in slope-intercept form is y is equal to mx plus b where m is the slope and b is the y-intercept. Now in this problem right here they tell us the slope. Similarly the form ymxa means slope m and y-intercept a.