Answer
700 J of energy is transferred from the system as heat.
Work Step by Step
We can find the energy $Q$ that is transferred to or from the system as heat as:
$\Delta U = Q + W$
$Q = \Delta U - W$
$Q = (-200~J) - 500~J$
$Q = -700~J$
The negative sign means that 700 J of energy is transferred from the system as heat.
