Find the dimensions of a rectangle whose width is 8 miles less than its length and whose area is 105 square miles

Area of a rectangle = w*l

w = width

l = length

In our problem,

Area = 105mi^2

l = x

w = x - 8

Let's plug our values into the formula above.

105mi^2 = x(x - 8)

Distribute the x

105mi^2 = x^2 - 8x

Subtract 105mi^2 from both sides.

0 = x^2 - 8x - 105

Let's factor the right side.

0 = (x - 15)(x + 7)

Set both terms equal to 0

x - 15 = 0

Add 15 to both sides.

x = 15

x + 7 = 0

Subtract 7 from both sides.

x = -7

Since the length cant be a negative number, 15 is the correct answer.

Length = x = 15 mi

Width = x - 8 = 15 - 8 = 7 mi