# Two sets

Suppose Set B contains 69 elements and the total number elements in either Set A or Set B is 124. If the Sets A and B have 29 elements in common, how many elements are contained in set A?

Result

A =  55

#### Solution:

$B = 69 \ \\ AB = A\cap B \ \\ AB = 29 \ \\ B_{ 1 } = B - AB = 69 - 29 = 40 \ \\ T = 124 \ \\ \ \\ A = T - AB - B_{ 1 } = 124 - 29 - 40 = 55$

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