A two-digit number and the number formed by reversing its digits add up to 121. Its tens digit is 3 more than its units digit. What is the number?

Explanation

1. 01

   Number + reverse = $11(a + b) = 121$, so $a + b = 11$.

2. 02

   $a - b = 3$ gives $a = 7$, $b = 4$.

3. 03

   The number is 74 (check: $74 + 47 = 121$).