Question

How many subsets does set a have if the set a has 3 elements? 3 6 8?

Answer 1

Consider a set {a,b,c} 
The 8 subsets are { }, {a}, {b}, {c}, {a,b}, {a,c}, {b,c} and {a,b,c}. 
If a set has n elements, the number of subsets is 2^n.

Answer 2

This should help

Let's say Set A = {1,2,3}, Set A can have subsets of:

{1}, {2}, {3}, {1,2}, {1,3}, {2,3}

And so there is 6 subsets.