Which of the following is the correct sum of 12 and 9?

Step-by-step solution

1. Add the units digits: $2+9=11$; write down $1$ and carry over $1$.
2. Add the tens digits plus the carry: $1+1+1=3$; write down $3$.
3. Hence the sum is $31$, but we must check the options for the correct answer.

Concept tested: Basic addition of two-digit numbers

Published 1 October 2026 · How this solution was prepared and checked