The equation is already solved for y
It's in y = mx+b form where
m = -3 = slope
b = 1 = y intercept
The graph is shown below. It's a straight line through the two points (0,1) and (1,-2).
Note that (0,1) is the y intercept. We use the slope = -3 = -3/1 to move 3 units down and 1 unit to the right to arrive at (1,-2).