CREATE TABLE table_name_51 (crude_death_rate__per_1000_ INTEGER, deaths VARCHAR, crude_birth_rate__per_1000_ VARCHAR)
Which Crude death rate (per 1000) has Deaths of 768, and a Crude birth rate (per 1000) smaller than 29.7?
SELECT MIN(crude_death_rate__per_1000_) FROM table_name_51 WHERE deaths = "768" AND crude_birth_rate__per_1000_ < 29.7