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 enjoy = Donkey that work

Equation 2

Man = eat + sleep + earn money

Donkeys = eat + sleep

Therefore,

Man = Donkeys + earn money

Therefore,

Man - earn money = Donkey

In other words,

Man that don't earn money = Donkey

Equation 3

Woman = eat + sleep + spend

Donkey = 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

Man that don't earn money = Woman that don't spend.

So, Man earn money not to let woman become Donkey! (Postulate 1)

And, Woman spend not to let man become Donkey! (Postulate 2)

So, we have:

Man + Woman = Donkey + Earn money + Donkey + Spend money

Therefore - from Postulates 1 and 2, we can conclude

Man + Woman = 2 Donkey that live happily together!