To determine Iy in the circuit, understanding the configuration of resistors in series and parallel is essential. The current arrow for Iy should be correctly positioned according to the problem's specifications, as it affects calculations. Applying Kirchhoff's current law can help clarify the relationships between currents at nodes. The user has already calculated Vx using voltage division but struggles with finding Iy specifically for the 40-ohm resistor. Providing more detailed work or calculations may yield better guidance from others in the discussion.