If a very complex closed system has 200 J of energy in it, then the energy converts from 1 form to another to another to another. How much energy should the system still have at the end?

At the end the energy of the system is the same as 200 J.

Explanation:

It is a closed complex system and it has 200 J of energy.

Here the system is converting from one form to another form and then to another form.

As we know that there is a conservation of energy when one form is converted to another form without losing or gaining energy, whereas it may convert from one form to another form with the energy being conserved.

So after there is a conversion of one form to another form but there is no loss or gain of energy and same energy must be retained.

it is the most commonly accepted one