A rectangle watch of ground is 5 m longer than it is wide its area is 20,000 m²

Lets call x how wide it is, and write the area equation:

area = width*length

a = (x) (x + 5) = 20000

expand it:

x^2 + 5x = 20000

make a quadratic trinomial:

x^2 + 5x - 20000 = 0

lets apply the general quadratic formula to solve:

x = (-5 + - √ (25 + 80000)) / 2

x = (-5 + - 282.89) / 2

we take the positive solution:

x = (-5 + 282.89) / 2

x = 138.94

therefore the rectangle width is 138.94 m and 143.94 m long