SOLUTION: The sum of all the natural numbers from 200 to 600 (both inclusive), which are neither divisible by 8 nor by 12, is

1.  Find the sum S1 of all the natural numbers from 200 to 600 (inclusive).



2.  Find the sum S2 of all natural in this range that are multiples of 8 or 12.

    Then subtract this sum S2 from S1 to get the answer.



3.  To find the sum S2, first find the sum S8 of all the natural integers in the range multiples of 8.

    Then find the sum S12 of all the natural integers in the range multiples of 12.

    Then add S8 and S12.

    Then find the sum S24 of all the natural in the range that are multiple of 24.

    Then S2 = S8 + S12 - S24.



4.  You got all the instructions.

    Since you came with the problem which is the School Math (+) level, these instructions should be enough to you.