my pc is a laptop ... can i use the hole with headphones as linein ? 
No you can't use the socket for headphones because that's an output socket, your mixer must be connected to an input like Line-In or Microphone (all laptops have Microphone or Line-In, some both.
You can use the Mic-in (pink socket) instead of Line-In, if your laptop does not have Line-In.. only problem is that the recording quality probably is much worse.. so basically if you want full sound quality you need an external soundcard.
Sure you have it but i own it.. and it's the best solution and quality for you
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