title: Write logic gates from logic gate circuit
body: <p>Could someone please show me how to write the logic from this logic circuit?</p>
  
  <p><img src="https://i.stack.imgur.com/QE5wa.jpg" alt="enter image description here"></p>
  
  <p>Following you guys' explanation, I have these results, am I right: </p>
  
  <p><img src="https://i.stack.imgur.com/xHutB.jpg" alt="enter image description here"></p>
  
  <p>The question is which one of a, b, c, d produces the same ouput as the first circuit. I don't see any similar results here, please illuminate me !</p>