First we state that girls require time and money.
Girls = Time x Money
And as we all know, "Time IS Money".
Time = Money
Therefore
Girls = Money x Money (Money)²
And because "Money is the root of all evil"
Money = √Evil
Therefore
Girls = (√Evil)²
And we are forced to conclude that
Girls = Evil
Note: For lack of a better character, in the example above, the character
√ is the symbol for "Square Root".