You can add multiple positive/negative voltage sources together with a difference amp with several differential summing stages.
Scaling can also be used with different resistors. Analog addition WITHOUT inverting stage first.
-7V shows an Ex of a large Common Mode.
Switch on 6v shows capability of floating inputs. 10K(fb)/20K ohm resistors shows weighting ability on input.
Vout = 6/2 + 7 +1= 11v.
Warning: All sources become parallel resistors - Low impedance circuit! Make resistance high.
Warning: IF the V+ and V- node of op amp is BELOW minimum rail (GND) then the simulation will still work, but will NOT work in real life.
