Basics of J-K Flipflop when J=K=1 :-
CLK=0 ===> previous values as o/p
CLK=1 ===> toggle the previous values as o/p
∴ Q0N = Q0' ( CLK ) value changed from 1 --> 0 ( Because -ve edge triggering )
∴ Q1N = Q1' when ( Q0N and CLK ) value changed from 1 --> 0 ( Because -ve edge triggering )
= Q1 otherwise
for avoiding confusion, take a temporary clock as Q0N and CLK
∴ Q2N = Q2' when ( Q0N and Q1N and CLK ) value changed from 1 --> 0 ( Because -ve edge triggering )
= Q2 otherwise
for avoiding confusion, take another temporary clock as Q0N and Q1N and CLK
By the above information
Q0 Q1 Q2
-----------------------
0 0 0
1 0 0 ( after applying 1st clock pulse )
0 1 0 ( after applying 2nd clock pulse )
1 1 0 ( after applying 3rd clock pulse )
0 0 1 ( after applying 4th clock pulse )
1 0 1 ( after applying 5th clock pulse )
After 5 clk pulses, 101 (Q0,Q1,Q2) and Y=0 (Q0⊕Q1⊕Q2)