With 5 elements in A={20,1,6,10,11}, there are 2^5=32 possible subsets, including the null set, and A itself. Any subset that is identical to A is NOT a proper subset. Therefore there are 31 proper subsets, plus the subset {20,1,6,10,11}.
The subsets are: null set {} (has no elements) ........total 1 {20},{1},{6},{10},{11}.......................total 5 {20,1},{20,6}...{10,11}.....................total 10 {20,1,6},{20,1,10},...{6,10,11}.........total 10 {20,1,6,10}...{1,6,10,11}.................total 5 {20,1,6,10,11}.................................total 1 Altogether 32 subsets.
