
### Instruction: help me answer this question If S and T are two sets such that S has 21 elements, T has 32 elements, and S ∩ T has 11 elements, how many elements does S ∪ T have?, think step by step
### Assistant: Using the formula n(S ∪ T) = n(S) + n(T) - n(S ∩ T) , we find n(S ∪ T) = 42 , The answer is n(S ∪ T) = 42
