Final answer:
The subnet address for the IPv6 address 2001:DB8:BC15:A:12/64 is 2001:DB8:BC15:A:0:0:0:0, which includes the first 64 bits of the given address.
Step-by-step explanation:
The question asks about finding the subnet address for an IPv6 address. Given the address 2001:DB8:BC15:A:12/64, we can determine the subnet address by looking at the first 64 bits of the address (since the subnet prefix length is 64). Therefore, the subnet address is the same as the first 64 bits of the given address, which is 2001:DB8:BC15:A:0:0:0:0. This represents the starting address of the subnet. All addresses within this subnet will have the first 64 bits in common.