\( \Large x^{2} - 16 = 0 \)

=> \( \Large x^{2} = 16 = x = \sqrt{16} = \pm 4 \)

and \( \Large y^{2} - 9y + 20 = 0 \)

\( \Large y^{2} - 4y - 5y + 2 = 0 \)

=> \( \Large y \left(y-4\right) - 5 \left(y-4\right) = 0 \)

=> y = 5, 4

\( \Large y \ge \  x \  or \  x \le y \)