Hi.
21990=(1+1)1990
=>1990C0+1990C1+1990C2+.......+1990C1989 + 1990C1990
=>1 + 1990C1 + 1990C2........1990C1989 + 1
Now except for the first and last terms all terms are divisible by 1990
{all will have 1990! in the numerator which is obviously divisible by 1990}
=> so when you divide 2 by 1990 the remainder is
2 