P Q R P=>Q Q=>R P=>R
0 0 0  1    1    1
1 0 0  0    1    0
1 0 1  0    1    1
1 1 0  1    0    0
1 1 1  1    1    1
0 1 0  1    0    1
0 1 1  1    1    1
0 0 1  1    1    1

P=>Q
Q=>R
----
P=>R