I assume the question asks for the formula for finding the number of subsets in a set.
This is the formula for finding the number of subsets in a set.
[tex] 2^{n(A)}[/tex]
- n(A) means number of elements in A.
Ex.
A = {a, b, c}
There are 3 elements, so [tex] 2^{3} [/tex] = 8 subsets all in all
Proof:
Subsets: B = {a} C = {b} D = {c} E = {a, b} F= {a, c} G = {b,c}
H = {a, b, c} I = { }
(Though, you can just make the formula, [tex] 2^{n} [/tex] where n is the number of elements in the set)