Q. The number of triplets $(A, B, C)$ where $A, B, C$ are subsets of $X=\{1,2,3, \ldots \ldots, 100\}$ such that $A \cap B \cap C=\phi$ but $A \cap B \neq \phi$ and $B \cap C \neq \phi$ is
Permutations and Combinations
Solution:
For each elements there are 7 choices without any restriction $7^{100}$.
