Using Superposition , find the voltage across Is for the network below ?

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The answer is 10.66 I just need the way explain the steps with diagram thanks 
Using Superposition , find the voltage across Is for the network below ?RS10. 660Mr4.12+ V. -R227Mr- 12 VMr-06 12Is = 6 A4 02+ & VR3 2. 30 12 RX $ 12.121| Show your work : formula , substitute given , and write the final answer on the blank