"The square of the sum of the number and 25 is equal to 36" translates to
[tex](n+25)^2=36[/tex]
Take square root of both sides:
[tex]|n+25|=6\quad\Longrightarrow\quad n+25 = 6\ \text{ or }\ n+25=-6[/tex]
Then subtract both sides by 25:
[tex]n = 6-25\ \text{ or }\ n=-6-25\\\ \\\boxed{n=-19\ \text{or}\ n=-31}[/tex]
Hope this helps.
