real numbers
2.77 is not a natural number (counting numbers 1, 2, 3, ...)
2.77 is not a whole number (non-negative integers 0, 1, 2, 3, ...)
2,77 is not an element of null set as a null set has no elements.
{5, 7, 9}
The elements 5, 7 and 9 are elements of set D and they are also elements of set E.