Ans is 8
if subnet ID bit is n then , max no of possible subnets are 2^n
In our case subnet ID bits are 3 therefore total subnet possible are 8 .
We can use all the subnets no restriction on it , In gate we should pay more attention to the question wordings if there is some supposition or rules or convention they are mentioned in the question if not then stick to the concept
Yeah per subnet no of usable IP = no of IP address possible -2