This is a fake function question. This means, they make up some weird symbol you've never seen before, and hope you get scared off by it. However, these are easy, so you definitely shouldn't run away. They must define it for you. Just follow instructions and be careful.
In this case, we just need to find the 2nd and 3rd positive multiples of 5 and add them. The first positive multiple of any number is the number itself. I keep saying positive because 0 is also a multiple of 5; in fact, it's a multiple of everything. Anyway, the 2nd multiple of 5 is 10, and the third is 15. Thus, since 10 + 15 = 25, A is the answer.
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