This is an old favorite of mine...

Can you find the answer?


  • $\begingroup$ I am damn sure that this is a duplicate question. I have seen the same question here at the early stages of the puzzling.stackexchange. $\endgroup$ – AeJey Mar 31 '16 at 13:12




As $(x-x)=0$ and $0$ multiplied by any number is $0$.

| improve this answer | |
  • $\begingroup$ Oh you posted just seconds before I did. I'll remove my answer. $\endgroup$ – Ghapla Mar 31 '16 at 10:22

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