Networking help about subnetting

Hello everyone I recently started an academy online at network administration and we got a task for practice now I have absolutely no clue on how to do this are there any tips or tutorials u can give me ?

1. 10.20.6.0. / 24 split on different networks in a way that every network has a minimum of 7 Computers.

a) Find the possible number of adress hosts in every subnet

b) Find the possible number of subnets

1. Find the common Network ID for 111.17.0.0. /24

- 111.17.1.0. /24

-111.17.2.0. /24

- ...

- 111.17.9.0. / 24

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Mainly my problem is the first sentence split 10.20.6.0 /24 on different networks in a way that every network has minimum of 7 Computers. I figured which formula I have to use 2 on the power of n minus 2 for host adresses but how am I suppose to split the network ? Thanks in advance.