Answer:
25/144
Explanation:
We presume the probability is proportional to the area. That is, darts are uniformly distributed over the large square. (We know that's not the case, but it is the only way we can work the problem with the given information.)
The area of the smaller square is 5² = 25. The area of the larger square is 12² = 144.
The ratio of the two areas is the probability of hitting the small square:
25/144