Jawabanmu

2014-05-25T17:38:36+07:00
N(A∪B) = (N(A) - N(A∩B)) + (N(B) - N(A∩B)) + N(A∩B)
54 = (38 - N(A∩B)) + (31 - N(A∩B)) + N(A∩B)
54 = 38 - N(A∩B) + 31 - N(A∩B) + N(A∩B)
54 = 69 - 
N(A∩B)
N(A∩B) = 69 - 54
N(A∩B) = 15