Equation 1

Human = eat + sleep + work + enjoy
Donkey = eat + sleep

Therefore,
Human = Donkey + work + enjoy

Therefore,
Human - enjoy = Donkey + work

In other words,
Human that don't know how to enjoy = Donkey that work
============ ========= ========= ========= ========= ===

Equation 2

Men = eat + sleep + earn money
Donkeys = eat + sleep

Therefore,
Men = Donkeys + earn money

Therefore,
Men - earn money = Donkeys

In other words,
Men that don't earn money = Donkeys
============ ========= ========= ========= ========= ====

Equation 3

Women = eat + sleep + spend
Donkeys = eat + sleep

Therefore,
Women = Donkeys + spend

Therefore,
Women - spend = Donkeys

In other words,
Women that don't spend = Donkeys
============ ========= ========= ========= ========= =====

To Conclude:

From Equation 2 and Equation 3
Men that don't earn money = Women that don't spend.

So, Men earn money not to let women become Donkeys! (Postulate 1)

And, Women spend not to let men become Donkeys! (Postulate 2)

So, we have?
Men + Women = Donkeys + earn money + Donkeys + spend money

Therefore from postulates 1 and 2, we can conclude,
Man + Woman = 2 Donkeys that live happily together!