If you would like to cube one number and make it bigger than 200 but smaller than 400, you can find the number using the following steps:
n ... the number
200 < n^3 < 400
For example:
If n equals to 6, then n^3 = 6^3 = 6 * 6 * 6 = 216 and 200 < 216 < 400, so the result could be 6.
If n equals to 7, then n^3 = 7^3 = 7 * 7 * 7 = 343 and 200 < 343 < 400, so the result could also be 7.
But, if n is 8, then n^3 = 8^3 = 8 * 8 * 8 = 512 and 512 > 400.
Result: You can take the numbers 6 and 7.