x-y=-2 is a linear graph (straight line). To draw the line we only need two points and typical points are the two intercepts. To find out what they are set one variable to zero and solve for the other variable to find its intercept.
When x=0, -y=-2 so y=2 is the y-intercept (0,2).
When y=0, x=-2 so x=-2 is the x-intercept (-2,0).
The line through these two points is the required graph.