CREATE TABLE table_name_25 (date_of_vacancy VARCHAR(255), position_in_table VARCHAR(255), outgoing_manager VARCHAR(255))
what is the date of vacancy when the position in table is 16th and the outgoing manager is russell slade?
    
SQL: SELECT date_of_vacancy FROM table_name_25 WHERE position_in_table = "16th" AND outgoing_manager = "russell slade"