This equation is in slope-intercept form, which is y= mx+b, where "m" is the slope and "b" is the y-intercept.
In this case, the slope (m) is -3 and the y-intercept (b) is 15.
To graph this equation, start by plotting the y-intercept, which is (0,15). From there, use the slope to find other points on the line.
To do this, you can use the slope to find the rise and run from the y-intercept. Since the slope is -3, the line goes down 3 units for every 1 unit over to the right. So, for example, from (0,15) you can go down 3 units to (1,12) to get another point on the line.
Repeat this process to find more points, and then connect them with a straight line.