List the members of P (fa, b, c, d}). Which are proper subsets of fa, b, c, d) ?

Answer: As i understand, the set is P = {a, b, c, d}

then all the proper subsets are all the sets that belongs to P, that are different of P. Then A is a subset of P if all the elements of A belongs to P, but A is not equal to P

this is:

the sets of one element : {a}, {b}, {c}, {d} and the null set; ∅

sets of two elements: {a, b}, {a, c}, {a. d}, {b, c}, {b, d}, {c, d}

sets of three elements : {a, b, c}, {a, b, d}, {a, c, d}, {b, c, d}

and there arent sets of 4 elements or more.