Final answer:
The assembly code 'add x30, x5, x6' adds the hexadecimal values in registers x5 and x6 which results in an overflow and the value 0x5000000000000000 for x30.
Step-by-step explanation:
The question involves understanding an assembly language instruction for an arithmetic operation between two register values. When the instruction add x30, x5, x6 is executed, it adds the values in registers x5 and x6, and stores the result in register x30. In this case, we are adding two hexadecimal numbers, 0x8000000000000000 and 0xD000000000000000. When performing this addition, the result is 0x5000000000000000, due to the overflow that occurs with unsigned integers in most assembly languages.