Looking to use an Op-Amp to scale a high-voltage system to a low voltage system
So you want linear scaling with 9V output when 30V input, and 14V output when 120V input, correct? Vout = (Vin * 5 / 90) + (22/3). My first thought was can you use a non-inverting configuration with the inverting input reference at 7.3V?

However can't get less than unity gain with non-inverting configuration. So take an inverting op amp configuration to get the 5/90 gain, then use a second stage to invert again and add the offset. The offset is a negative voltage because the second stage is an inverting adder.







simulate this circuit &ndash; Schematic created using CircuitLab

You can click on the link that says "simulate this circuit", and try it yourself.

Some caveats:

120V is a hazardous voltage, use appropriate precautions.

120VAC has peak voltages that are higher than the RMS average of 120Vrms, the actual peaks are almost +150V / -150V. For this simulation I assume you mean 120V DC not AC. Still hazardous though, so use sensible precautions. 

The high voltage will be across R1 because node V1 is driven to virtual ground.

I'm assuming that the op amp is powered before the 30VDC..120VDC signal is present. The question requirements are a bit vague. If the 120VDC might be present before the op amp power supplies are stable, then it would be more robust to use a resistive divider first (since less than unity gain!) and then the summing amplifier.

This all gets a lot easier if there were a way to avoid the offset voltage, perhaps just use an ADC with a suitable resistor divider input. Hard to tell what's the best approach given the limited information. But there are definitely ways to accomplish what you're trying to do.