Question

Determine Vout/Vin for the circuit (see below) if we assume the operational amplifier is perfect

Answer 1

Have you determined if the feedback is positive or negative?

Answer 2

Hint. It is negative feedback. Also note that Vout is reduced by the voltage divider consisting of the 5K and 10K resistors. Since no value of Vin is provided, you will need to express Vout in terms of Vin.

Answer 3

@radar
1 + Rf/Ri.
In this case thats 1 + 20k/20k = 2. But that is to the output of the opamp.

Then there is a voltage divider, so 2 * 10/15 = 1.333

Gain = 1.333 right?

Answer 4

That is what I would of gotten. Good luck with you studies. I haven't messed with that for years and may have overlooked something, but I think you've nailed it.