Nio is 20 years old and his brother Miguel is 8 years old. How old was Miguel when Nio is only 15?

[math_celebrity]

Nio is 20 years old and his brother Miguel is 8 years old. How old was Miguel when Nio is only 15?

Nio is 20.
20 - 15 is 5 years ago.

So Miguel's age 5 years ago is:
8 - 5 = 3