CREATE TABLE table_name_21 (tackles VARCHAR(255), yards VARCHAR(255), fumr VARCHAR(255), totaltk VARCHAR(255))
what is the total number of tackles when fumr is 0, totaltk is 54 and yards is less than 0?
    
SQL: SELECT COUNT(tackles) FROM table_name_21 WHERE fumr = 0 AND totaltk = 54 AND yards < 0