No experienced person is incompetent. Jenkins is always blundering. No competent person is always blundering. Therefore Jenkins is inexperienced.
(1) No experienced person is incompetent.
(2) Jenkins is always blundering.
(3) No competent person is always blundering.
(4) If a person is always blundering, then that person is not competent (by contraposition from 3)
(5) Jenkins is not competent (from 2, 4 by MP If blundering, then not competent and Jenkins is blundering therefore Jenkins is not competent.)
(6) If someone is incompetent, they cannot be experienced. (by contraposition from 1)
(7) Jenkins is not experienced (from 5, 6 by MP If incompetent, then not experienced and Jenkins is not competent therefore Jenkins is not experienced.)
All X are Y,
Z is X
Therefore Z is Y.