2+2=4

Correct. 2 + 2 = 4.

If you want a quick justification: in Peano arithmetic, 0, 1 = S(0), 2 = S(1) = S(S(0)). With addition defined by a + 0 = a and a + S(b) = S(a + b), we get 2 + 2 = 4.

Would you like a short practice set or a deeper dive into a proof using a specific axiom system? Here are a few addition problems to try:

• 3 + 5 = ?
• 6 + 7 = ?
• 0 + 9 = ?
• 10 + 10 = ?
• 12 + 3 = ?

Answers: 8, 13, 9, 20, 15.