Question

The length of a rectangular field is 20 less than its width. The area of the field is 12,00 square feet. What is the width of the field?

Answer 1

x(x-20)=12000
x^2 - 20x = 12000
x^2 - 20x - 12000 = 0
(x - 120)(x + 100) = 0  

x = -100, 120

so the width is 120 ft