In the circuit configuration of figure given below the output voltage (V_o1 - V_o2) is: 

Concept:

Op-amp:

• It has high input impedance,low output imepedence.
• By using negative feedback, virtual ground theory is applicable that is  V^-  = V^+.   

Calculation:

By virtual ground, opamp will have voltage V₁ and V₂  at negative terminal.

and opamp has zero input current(it has high input impedence).

current I in 10k register is :

I=\(\frac{V_1 - V_2} {10k}\)

now we can write the equation:

-V₀₁ + 20k × I + 10k × I + 20k × I + V₀₂ = 0

V01  - V02 = 50k × I 

V01  - V02 = 50k ×  \(\frac{V_1 - V_2} {10k}\) ( by putting I value)

V01  - V02 = 5(V1 - V₂)

so correct option is 3.