A union B union C = A + B + C - A inte B - A inter C - B inter C + A inter B inter C, where inter is intersection
Also A union B = A + B - A inter B
Given Originally
A union B = 16, A union C = 17, B Union C = 18
Statement 1:
Gives us A inter B inter C = 9
So question cannot be answered alone with this statement.
Statement 2:
Gives us A, B, & C.
This alone cannot answer the question. However with the help of A, B & C and A union B = 16, A union C = 17, B Union C = 18, we can obtain A inte B, A inter C, and B inter C using formula mentioned in line 2 above.
Combining both statments:
We have all the things needs for calculation of A union B union C.
Answer C.