Chapter 3.2, Problem 19P

In each of Problems $15$ through $20$:

(a) Find the equilibrium solution, or critical point, of the given system.

(b) Use a computer to draw a direction field and phase portrait centered at the critical point.

(c) Describe how solutions of the system behave in the vicinity of the critical point.

$x\text{'}=x+y-3$, $y\text{'}=-x+y+1$