The sum of 3, 7, and a number amounts to 16

The sum of 3, 7, and a number amounts to 16

Let the number be n. A sum means we add. We're given:
3 + 7 + n = 16

Grouping like terms, we get:
n + 10 = 16

Typing this equation into our search engine, we get:
n = 6