Final answer:
The next whole number after 7DD in the base-14 system is 7DE, assuming 'D' represents thirteen.
Step-by-step explanation:
The student has asked to write the next whole number after 7DD in the base-14 system.
It's similar to the decimal system, where if you add one to the last digit and it exceeds the base, it resets to zero and the next significant digit is incremented.
Here 'D' in base-14 is equivalent to 13 in the decimal system and since it's the highest single-digit number in base-14, adding 1 to 'D' will require us to increment the next significant digit.
To proceed, we need to follow the base-14 counting, which after 'D' goes to '10', so '7DD + 1' in base-14 is '7DE'.