Hi I really need help with this too! I cannot see where I went wrong, really. Thank you so much in advance! Really need this!
! I've attached the question itself and my attempt to find P(D) to which I failed.
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Thank you so much!
I didn't know that P(C|D)+P(C|D') = P(C)!
If I expand it out eg. P(C|D)P(D) = P(CnD), it will be quite different from P(C|D')P(D') = P(CnD') so I dont think that's the proof..
Could you teach me how to prove P(C|D)+P(C|D') = P(C) using any method or even the venn diagram?