2 1+ 16 = 37 (days)

A: The summer vacation lasts for 37 days from July 1 1 to August 16.

Ideas:

How many days are there in July? The holiday starts at 1 1. There is no school at 1 1, so it is necessary to add 1, 3 1 1 = 265438.

How many days are there in August? From August 1 to August 16, there is 16-0 = 16 (days) (this step can be omitted).

1* * vacation days: 2 1+ 16 = 37 (days)