Arectangle field has an area of 300 square meters and a perimeter of 80 meters. what are the length and width of the field?

By definition the area of a rectangle is:
 A = w * l
 The perimeter is:
 P = 2w + 2l
 Where,
 w: width
 l: long
 Substituting values:
 300 = w * l
 80 = 2w + 2l
 Solving the system of equations we have:
 l = 30 m
 w = 10 m
 
 The length and width of the field are:
 l = 30 m
 w = 10 m