Question

A wall is 12 feet long and 8 feet tall. There is a square window 4 feet long in the wall. What is the area of the wall surface?

Answer 1

A=LxW
L=12
W=8

12x8=96ft. 
Area = 96ft (without the window.)

Now we need to subtract the window from the area from the wall. What is the area of the window?

A=LxW
L=4
W=4

4x4=16
A=16ft (Area of just the window)

Let's subtract the window form the wall to get the total area!

96-16=80ft

A=80ft