I need help with graphing inequalities with constraints

Question

I have a test review on graphing inequalities with constraints. It is 

 

P=4x-3y   

 

Constraints:

x>=1

y>=2

x+y<=10

x-y>=-4

 

I got 3 of the 4 corners (1,2) (1,5) and (8,2).  I need to find the fourth to get credit for my work.  

Answer 1

(3,7) is the 4th point

it's the intersection of x+y= 10 and x-y=-4

add them to get 2x = 6, x=3

3+y=10

y = 7