Arectangular garden has a perimeter of 48 cm and an area of 140 sq. cm. what is the width of this garden?

We can call a the width of the garden and b the length of the other side. 
The perimeter of the garden is the sum of the two sides, and it is equal to 48 cm:
(1)
The area of the garden is the product between the two sides, and it is equal to :


From (1), we find

And by substituting this into (2) 


which gives two solutions:
, to which corresponds 
, to which corresponds 

So, the width of the garden is  while the length of the other side is .