I saw a shirt for $97.
I borrowed $50 from mom and $50 from dad.
I bought the shirt and got $3 change.
I returned $1 to mom, and $1 to dad, and kept $1 for myself.
Now I have to return $49 to mom and $49 to dad.
$49 + $49 = $98 + my $1 = $99
Where did the other $1 go ?