If w meters is the width, the the length is (w+5) meters. The area equation is w * (w+5) = 50. (*) You can solve this quadratic equation w^2 + 5w - 50 = 0 using factoring (w-5)*(w+10) = 0, which gives you a unique positive solution w= 5. Or you can guess the answer in 5 seconds, looking into equation (*). The width is 5 meters, the length is 5+5 = 10 meters, and the perimeter is 5 + 10 + 5 + 10 = 30 meters.