Which Crude death rate (per 1000) has Deaths of 768, and a Crude birth rate (per 1000) smaller than 29.7?
CREATE TABLE "registered_births_and_deaths" (
  "average_population_x_1000" real,
  "live_births" text,
  "deaths" text,
  "natural_change" text,
  "crude_birth_rate_per_1000" real,
  "crude_death_rate_per_1000" real,
  "natural_change_per_1000" real
);
SELECT MIN("crude_death_rate_per_1000") FROM "registered_births_and_deaths" WHERE "deaths"='768' AND "crude_birth_rate_per_1000"<29.7;