If in an ideal op amp has no current coming out of the inverting terminal and the non-inverting terminal then shouldn't the current going through the 9k Ω resistor be equal to 1mA and also can't the 15k and 6k ohm resistor be combined in parallel so that the KCL at the output node would just be the current from the 9k ohm and the combined 15k and 6k?