Yes because 3 times 6 = 18
Yes, it is.
Supplements are defined in a context. Without the context there cannot be an answer and "Math" does not provide enough context.
18
Not if you are under 18.
The math factor pairs of 18 are (1,18) , (2,9) , (3,6) .
Without parental consent you would have to be 18
18 and be able to pay for it.
18.4286
if you were homeschooled then you should be able to attend college.
6
2
18,19,26,3
There is no special name: just "18 percent".