You can put this solution on YOUR website! .
How many subsets of {3, 7, 11, 12} have 11 as a member? (Calculate
this without listing the subsets.)
~~~~~~~~~~~~~~~~~~~~~~~~`
It is the same as to ask
How many subsets are in the set {3, 7, 12}?
The answer is = 8.
The number of subset of the finite set containing N elements is
(including the set itself as a subset and the empty subset).
See the lesson How many subsets are there in a given finite set of n elements? in this site.
