X and Y are two sets such that nX = 15, nY = 12 and n{X ∩ Y} = 7. Find n{X ∪ Y}.

Answer Details

The formula for finding the number of elements in the union of two sets X and Y is:

n(X U Y) = nX + nY - n(X ∩ Y)

where nX is the number of elements in set X, nY is the number of elements in set Y, and n(X ∩ Y) is the number of elements in the intersection of X and Y. In this case, nX = 15, nY = 12, and n(X ∩ Y) = 7, so we can plug in the values into the formula:

n(X U Y) = 15 + 12 - 7
n(X U Y) = 20

So, the number of elements in the union of X and Y is 20.