2+2=4

Yes—that's correct: 2 + 2 = 4 in base-10.

A quick note you can use in exams:

• In general, addition is defined so that a + 0 = a and a + (b + 1) = (a + b) + 1 (Peano-style definition). From that, 2 + 2 = 4.
• In other bases:
  • Base 3: 2 + 2 = 11_3 (which is 4 in decimal).
  • Binary (base 2): 10 + 10 = 100_2 (which is 4 in decimal).

Want a short practice set or a quick refresher on addition rules (commutativity, carrying)? I can tailor it to your exam.