While it is possible to perform hexadecimal additions in the same way as in bases 2 and 10, that is with sum and carry, the extra mental arithmetic involved may be deemed unwarranted.
For example in hexadecimal F + D is C carry 1. That is 15 + 13 is 28 or 12 and carry 16.
Instead it is recommended that hexadecimal addition be carried out by converting the original number to base 2 or 10, carrying out the addition and converting the answer back to the required base.
Next: Binary Subtraction