Equation 2
Man = eat + sleep + earn money
Donkey = eat + sleep

Therefore:
Man = Donkey + earn money

Therefore:
Man-earn money = Donkey

In other words
Man who doesn't earn money = Donkey

Equation 3
Woman= eat + sleep + spend
Donkey = eat + sleep

Therefore:
Woman = Donkey + spend
Woman - spend = Donkey

In other words,
Woman who doesn't spend = Donkey

To Conclude: From Equation 2 and Equation 3
Man who doesn't earn money = Woman who doesn't spend

So Man earns money not to let woman become a donkey!
And a woman spends not to let the man become a donkey!

So, We have:
Man + Woman = Donkey + earn money + Donkey + Spend money

Therefore from postulates 1 and 2, we can conclude

Man + Woman = 2 Donkeys that live happily together!