Explanation: On plotting the constraints $x=3$, $x=9,\;x=y$ and $x+y=14$, we get the following graph. From the graph given below it clear that feasible region is $\text{ABCDEA}$, including corner points $A(9,0),\;B(3,0),\;C(3,3),\;D(7,7)$ and $E(9,5)$.Thus feasible region has 5 corner points including $(7,7)$ and $(3,3)$.