If P is the midpoint of BC then PB = 12 too and - most important - RB = 12 for symmetry reasons.
You now can determine the lengths of all sides:
AC= 25 + 12 = 37
BC = 12 + 12 = 24
AB = 25 + 12 = 37
That means you are dealing with an isosceles triangle with base BC = 24