This is one of those fun pseudo-mathematical proofs that you can find all over the internet. :-)

Girls are time and money: girls = time * money;
but, time is money: time = money;
which implies: girls = money * money;
which implies: girls = money^2;
but, money is the root of all evil: money = (all evil) ^1/2;
which implies: money^2 = all evil;
therefore, all girls are evil: girls = all evil.