For each donation not from a teacher, state the donor account id and calculate the percentage of donation given for optional support.
not from a teacher refers to is_teacher_acct = 'f'; donor account id refers to donor_acctid; percentage of donation = divide(donation_optional_support, donation_total)*100%
SELECT donor_acctid, donation_optional_support / donation_total FROM donations WHERE is_teacher_acct = 'f'