Problem Solving (PS) | There are twenty-five identical marbles to be divided among four broth

Hifiras92 can you further elaborate on the below point.

"Now the remaining 13 marbles must be distributed in such a way that any one can get any share

Consider the 13 marbles being separated by 3 separators such that there are four slots in all (representing the four brothers)

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We can arrange these 16 elements in\(\frac{16!}{13!3!}\) ways = 560 ways"

Thanks.