CREATE TABLE table_name_82 (ihsaa_class VARCHAR, _number___county VARCHAR, mascot VARCHAR)

Name the IHSAA class with county 18 delaware and tigers mascot
SELECT ihsaa_class FROM table_name_82 WHERE _number___county = "18 delaware" AND mascot = "tigers"
SELECT "ihsaa_class" FROM "table_name_82" WHERE "18 delaware" = "_number___county" AND "mascot" = "tigers"