Gain of an amplifier (electronics)?

I have worked out the gain of an amplifier, but I don't understand what to do from there. The circuit the question is based on is a non-inverting amplifier with an oscilloscope connected to the input and output. The input voltage is 3v. I have worked out using the gain equation that the gain is 5. Does that... show more I have worked out the gain of an amplifier, but I don't understand what to do from there. The circuit the question is based on is a non-inverting amplifier with an oscilloscope connected to the input and output. The input voltage is 3v. I have worked out using the gain equation that the gain is 5. Does that mean the output would be 5, or would it be 8. So basically, is the output equal to the answer of the gain equation, or do you add the result of the gain equation to the original voltage?

Thanks in advance. By the way I am doing AS level electronics.
Update: No for an non-inverting amplifier its Rf/R1 + 1. I am aware of the vout/vin, but to get vout you need gain, so you need the before-said equation (the one I use is simplified I know)
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