Number Problems

Step 1: Let the number be represented as , where is the tens digit and is the ones digit.
The sum of the digits is 12, so we have: When the digits are interchanged, the new number is . We are also told that this new number is 15 more than twice the original number, so:

Step 2: Solve the system of equations.
Simplify the second equation: Now, solve these two equations: Substitute into the second equation: Substitute into : Thus, the original number is .

Step 3: Conclusion.
The correct answer is (A) 39.