Question

Tom was in elementary school for 1997 to 2002 how much time was that in years

Answer 1

That's five years. Tom was in elementary school for five years.

Answer 2

1997-2000 is 3 years (1997-1998, 1998-1999, 1999-2000)
2000-2002 is 2 years (2000-2001, 2001-2002)
3+2= 5 years

Tom was in elementary school for five years