You don't have #15 included. If you meant to put #25, I already answered that. Here is the solution again though.
#25 is fairly simple. Plug in -4 and 3 into the equation, and the extraneous root will be the one that does not work.
[tex] \sqrt{12-(-4)} = \sqrt{16} = \frac{+}{}4[/tex]
Extraneous root in this case is positive four since +4≠-4
[tex] \sqrt{12-3} = \sqrt{9} = \frac{+}{}3[/tex]
In this case it's negative 3, since -3≠3
