Question

A={a,1,2,b,c}, how many of this clusters subset clusters includes 1 and c ?

Answer 1

I mean there is lower clusters of A like {1,2} or {a,1,2}. and I ask How many of these lower clusters include 1 and c?

Answer 2

i was thinking of maybe using combination to figure it out but not sure it'll work out right. write all the possible clusters and count lol

Answer 3

The right asnwer is 8, had 50 quesitons on test, I could not solve this...

Answer 4

I tried to do that: 2^n = A clusters lower clusters :D
so 2^5 = 32
and we we will do 32 - x then we will get unswer (x is here are the number of clusters that isn't include 1 and c :) )