Add 25 to both sides:
[tex] x^2 = 25 [/tex]
Square root both sides.
When you square root a perfect square, you will get a plus/minus result:
[tex] \sqrt{25} = \pm 5 [/tex]
[tex] x = \pm 5 [/tex]
[tex] \boxed{x = -5} \land \boxed{x = 5} [/tex]
The other solution to this answer is x = -5.
