Your numbers are the solutions to the quadratic equation
x(20-x) = 25
x^2 - 20x = -25 (multiply it out and multiply by -1)
(x-10)^2 = 75 (add 100 and factor the left side)
x = 10 ± 5√3 (take the square root and add 10)
The two numbers you seek are (10-5√3) and (10+5√3).
They are approximately 1.33975 and 18.66025
x(20-x) = 25
x^2 - 20x = -25 (multiply it out and multiply by -1)
(x-10)^2 = 75 (add 100 and factor the left side)
x = 10 ± 5√3 (take the square root and add 10)
The two numbers you seek are (10-5√3) and (10+5√3).
They are approximately 1.33975 and 18.66025