Solve the following addition and subtraction problems: 1 + 8 + 81 + 369 = ?

Solution:

1. Addition:

     369
   +  81
   -----

2. Step 1: Add the ones column: 9 + 1 = 10. Write down 0, carry over 1.
3. Step 2: Add the tens column: 6 + 8 + 1 (carry-over) = 15. Write down 5, carry over 1.
4. Step 3: Add the hundreds column: 3 + 1 (carry-over) = 4. Write down 4.
5. The result of 369 + 81 is 450.
6. Now add the remaining numbers: 1 + 8 + 450 = 459.

Final Answer: 459