I want to record guitar (using line cable) and my voice(using earphone's microphone) on my Dell laptop(which has only jack) both at same time. Is there any way to do it in the cheapest way? Thanks in advance.
All you need is an external sound card. See https://www.wirerealm.com/guides/top-10-best-audio-interfaces. The cheapest way is to find the cheapest one.