The base of an isosceles tiangle has a length of 25. what can you say about the lengths of the legs?

The sum of the lengths of any two sides of a triangle must be greater than the length of the third side (or else, it can't be a closed polygon). Since we know that the two sides in question are both of the same length in this case (since the triangle isosceles), their individual lengths must be greater than 25/2 = 12.5.