How do I find the area of JUST the garden?

Question

lifeisadangerousgame · Answer

A garden has a rectangular pond in the center. (See the drawing on the sheet found in the instructions.)

A.  Write and simplify an expression for the area of the whole figure. (10 points)

B.  Write and simplify an expression for the area of the pond.  (10 points)

C.  Write and simplify an expression for the area of just the garden.  (10 points)
(Working on C) 
I DO NOT by any means want the answer! Just how to do it! Thanks!

anonymous · Answer

outter rect -  inner rect

lifeisadangerousgame · Answer

Thank you! So all I have to do is get the area of the outer one and the inner one? How do I get the outer one?