The ground is effectively a current sink or source of infinite capacity so anything at a greater or lower potential than ground will flow current to or from the ground.

If the bottom connectors on V22 and V18 were connected together with a wire then they would have the same potential. However it also means that the current flowing out of V22 has to be the same as the current flowing into V18, and vice versa, because there is no way for current to enter or leave. Connecting both to ground also means they have the same potential, but it removes the requirement that the current flowing out of V22 has to be the same as the current flowing into V18, because ground can act as a current source or sink.

So treat the problem as if it was a closed circuit, but remember that you can't assume the current through V22 is the same as the current through V18.

The ground is effectively a current sink or source of infinite capacity so anything at a greater or lower potential than ground will flow current to or from the ground.

If the bottom connectors on V22 and V18 were connected together with a wire then they would have the same potential. However it also means that the current flowing out of V22 has to be the same as the current flowing into V18, and vice versa, because there is no way for current to enter or leave. Connecting both to ground also means they have the same potential, but it removes the requirement that the current flowing out of V22 has to be the same as the current flowing into V18, because ground can act as a current source or sink.

In this particular case the current flowing through V22 and V18 has to be the same because they're connected together by the top wire, so just treat the problem as if it was a closed circuit.