How many teachers have made some type of donation for projects in Chicago?
in Chicago refers to school_city = 'Chicago'; teachers refers to is_teacher_acct = 't'
SELECT COUNT(DISTINCT T2.teacher_acctid) FROM donations AS T1 INNER JOIN projects AS T2 ON T1.projectid = T2.projectid WHERE T1.is_teacher_acct = 't' AND T2.school_city = 'Chicago'