Final answer:
The number of Latin American countries that saw an improvement in their under-age-5 mortality rate between 1990 and 2011 is unknown.
Step-by-step explanation:
The question asks how many Latin American countries saw an improvement in their under-age-5 mortality rate between 1990 and 2011. To answer this, we need to look at the provided information. Although the information mentions infant mortality rates in Africa and low-income countries, it does not specifically mention Latin American countries. Therefore, we cannot determine the exact number of Latin American countries that saw an improvement in their under-age-5 mortality rate. Therefore, the answer to the question is unknown.