Answer
Total number of proper subsets are = 127
Work Step by Step
{X|X is a day of a week}
= {Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday}
A set of n elements have 2^{n} number of subsets.
Here set has 7 elements. So total number of subsets are 2^{7}=128.
As these 128 subsets also include the one subset which is the set itself. We need to exclude this one subset.
Thus Total number of proper subsets are = 128 - 1 = 127.
