The number of subsets on a set is given by the following formula:
Where n is the number of elements in the subset. 7 elements for this case.
That number of subsets calculated includes the set itself. N. If we wanted to calculate the number of proper subsets, we will need to subtract 1 from that formula, because the set N is not a proper subset of itself.
However, we are asked to find the number of subsets, and they are not specifying to find only the proper subsets, so we just need to use the formula above, recalling that n = 7.
There are 128 subsets in the set N.