Easy question: How old will Harry be in the year 2021?

Calculating Harry's Age:

Harry was 9 years old in 1990. This information allows us to determine his age in 2021 by adding the number of years between 1990 and 2021.

By doing a simple calculation:
2021 (current year) - 1990 (year Harry was 9) = 31

As we know, 31 years have passed from 1990 to 2021. So, if Harry was 9 in 1990, he would indeed be 40 years old in the year 2021.