We have,
U={1,2,3,4,5,6}
A={2,3}
B={3,4,5}
Now,
A′=U−A
={1,2,3,4,5,6}−{2,3}
A′={1,4,5,6}
B′=U−B
={1,2,3,4,5,6}−{3,4,5}
B′={1,2,6}
Hence, this is the answer.