We are to form two-digit numbers using the digits 0, 1, 2, 3, with repetition allowed, but the number cannot begin with 0. - Tens place (first digit): Cannot be 0 → Possible digits = 1, 2, 3 → 3 choices - Units place (second digit): Can be any of the 4 digits → 0, 1, 2, 3 → 4 choices Total numbers = 3 \times 4 = 12