# Find the smallest set A such that

Question:

Find the smallest set $A$ such that $A \cup\{1,2\}=\{1,2,3,5,9\}$.

Solution:

We have to find the smallest set A such that A $[\{1,2\}[\{1,2,3,5,9\}]$

The union of the two sets A & B is the set of all those elements that belong to A or to B or to both A & B.

Thus, A must be {3, 5, 9}.