First, we should find the total area of the wall, then subtract the area of the door since it's not getting painted.
Area= length x width
A= (12)x(18)
A= 216 square feet
Now for the area of the door:
A= l x w
A= (7)x(3)
A= 21 square feet
For the total area getting painted:
(Area of the wall) - (Area of the door) = (Total painted area)
216 - 21 = 195 square feet