If else statements using basic algebra

With this question and correct answer via codingbat, why is my answer wrong?

Q. Given an int n, return the absolute difference between n and 21, except return double the absolute difference if n is over 21.

diff21(19) → 2
diff21(10) → 11
diff21(21) → 0

Correct solution:

public int diff21(int n) {
    if (n <= 21) {
        return 21 - n;
    } else {
       return (n - 21) * 2;
    }
}

My solution:

public int diff21(int n) {
    if (n>21) {
        return (n-21);
    } else {
        return 2 * (12-n);
    }
}