
### Instruction: help me answer this question If X and Y are two sets such that X has 40 elements, X ∪Y has 60 elements, and X ∩Y has 10 elements, how many elements does Y have?, think step by step
### Assistant: This is derived from n(X ∪ Y) = n(X) + n(Y) - n(X ∩ Y) by substituting the given values and solving for n(Y). , The answer is Y has 30 elements.
