Answer:
Dimensions are 12 , 6
Explanation:
Forming algebraic equations and solving:
Let the length be 'x' miles.
width = (x - 6) miles
Area of a rectangle = length * width
x *(x -6) = 72 square miles
x*x - x *6 = 72
x² - 6x -72 = 0
Sum = -6
Product = -72
Factors = -12 , 6 { -12 * 6 = -72 & -12 + 6 = -6}
x² - 12x + 6x - 72 = 0 {Rewrite the middle term using the factors}
x(x - 12) +6(x - 12)=0
(x -12)(x + 6) =0
x - 12 = 0 ;
x = 12
{x + 6= 0 is ignored, as dimensions will not have negative value}
length = 12 miles
widht = 12 - 6 = 6 miles