Is this right?

[K.I.L.E.R]

!U = intersection
!(SET) = complement
U = union

A = {1, 2, 4, 5}
B = {2, 6, 7}
C = {1, 3, 7}
U = {1, 2, 3 .. 7, 9}

C !U (A U B)
= {1, 3, 7} !U {1, 2, 4, 5, 6, 7}
= {1, 7}

{1, 7, 9}
= C !U (B !U C) U (C !U A) U !(A U B U C)
= {1, 3, 7} !U {7} U {9}
= {1, 7, 9}

I'm just revising; I can't afford not to know this.