A Concise Introduction to Logic, Patrick J. Hurley, Wadsworth, 2006, 9th ed,. 8.7, III, 2 p. 448

Ronald Reagan was the oldest US president. Woodrow Wilson was a US president. Woodrow Wilson is not Ronald Reagan. Therefore, Ronald Reagan was older than Woodrow Wilson.

1.     Ur • (x)[(Ux • x ≠ r) ⊃ Orx] 2.     Uw 3.     w ≠ r ∴ Orw 4.     (x)[(Ux • x ≠ r) ⊃ Orx] • Ur 5.     (x)[(Ux • x ≠ r) ⊃ Orx] 6.     (Uw • w ≠ r) ⊃ Orw 7.     Uw • w ≠ r 8.     Orw

1 Com 1 Simp 5 UI 2,3 Conj 6,7 MP