how to understand "a" and "b"?
4) A number is divissssiiibbleeee? (Oops! Getting dizzy with all this testing) divisible by 5 when:
a) It goes to school and realizes it’s Sunday.
b) It goes to the laundry mat and drops its number, ending in half a dozen or zeros, or other digits.
c) It goes to a party that ONLY allows numbers that end in 0 or 5.

how to understand "ending in half a dozen or zeros, or other digits"?

Question

how to understand "a" and "b"?
4) A number is divissssiiibbleeee? (Oops! Getting dizzy with all this testing) divisible by 5 when:
a) It goes to school and realizes it’s Sunday.
b) It goes to the laundry mat and drops its number, ending in half a dozen or zeros, or other digits.
c) It goes to a party that ONLY allows numbers that end in 0 or 5.

how to understand "ending in half a dozen or zeros, or other digits"?

Answer

dozen = 12,   so half a dozen = 6
zeros = 0 or 00 or more
digits are any numbers between 0-9