Network 10.10.10.0/24 needs to be broken up into eight equal sized networks. Including the first and last networks, what subnet mask will be needed?

10.10.10.0/27 or 255.255.255.224

Explanation:

The network 10.10.10.0/24 has a default subnet mask of 255.255.255.0. To create eight equal sized networks, we have to take 3 bits from the host address to make subnets. The 3 bits is used to make 2³(8) subnets.

11111111.11111111.11111111.00000000  = 255.255.255.0 is the default subnet mask, if 3 bits is used to make subnets, the new subnet mask would be:

11111111.11111111.11111111.11100000 = 255.255.255.224

The subnet mask can also be represented as 10.10.10.0/27