One side of the back yard is usually the back side of the house.
But we won't worry about that ... we'll just go ahead and fence all
four sides, like you seem to have said.
Any rectangle has two sides that are the length and two sides that are the width.
So the distance around the back yard is
(14 + 14) + (12 + 12) = 52 meters.
(That's called the "perimeter" of the yard.)
If every meter of fence costs $9.00 , then 52 meters of fence will cost
(52) times ($9.00) = $468 . plus tax.
