The equation is in slope-intercept form #y=mx+b#, where #m# is slope and #b# is y-intercept.
Here, we do not see a visible slope , but it is #1/1#, or the parent linear function #f(x)=x#. Your y-intercept is #-23# because the equation can also be written as #y=x+(-23)\rArrx-23#.
Another method is to apply transformation rules . An equation with parameters #f(x)+a# or #y+a# would result in up/down shifting of coordinates, from the parent graph.
Your #a# is negative , so you will shift downwards. The simplest way is to take the origin point, plot it 23 units down from (0,0) or (0,-23), and then plot the other points accordingly based on the parent function #f(x)=x#.