Question

Please help me on this one its tough

Answer 1

A union B mean write a new set that includes everything of A and everything of B.
Ignore duplicates.

So if A was {1,2,3,4} and B was {1,2, 6, 10}
A union B is {1,2,3,4,6, 10} - this includes everything in A and also in B

A intersection B, you are only interested in the overlap between A and B (what is common between them?)
For my example, only 1 and 2 are elements of both A and B simultaneously
Therefore the set A intersection B is {1,2}

In your case the only numbers available are defined by your universal set U
C' means complement of C, so the numbers in the universal set U that are not in C.
A union B intersection C' means first find the union set of A and B, then find out what elements of this new set are common to the set C'.

The last one, A union (B intersection C') means find what is common to both B and C') then find the union of A and this new set.