Answer:
/27
Step-by-step explanation:
Subnet mask is a term used in computer science to describe a 32-bit number that is capable of "hiding", "hiding" an IP address, with the main purpose of dividing it into network addresses and addresses host. These addresses are reserved to be used for the most diverse purposes, which can be assigned to a host, or not, if so programmed.
In relation to the question above, if you need to use a subnet mask that accommodates 42 subnets and simultaneously the maximum number of hosts per subnet, you should use the "/27" mask. This mask will be able to supply 3 subnet bits. This will allow the creation of 8 subnets that will be responsible for meeting your requirement of seven, thus allowing the creation of a vast number of host/subnet addresses.