List numbers that leave remainder 4 when divided by 9, then check which also leaves remainder 1 when divided by 3.
• Numbers of the form 9k + 4: 13, 22, 31, 40, ...
• Check 13: 13 ÷ 3 = 4 remainder 1 ✓
• Check 13: 13 ÷ 9 = 1 remainder 4 ✓
The smallest possible number is 13.
Final Answer: 13