Hello
I believe that most of the answers to this lab are wrong.

e.g. Q5
66.66.0.0 to 66.66.15.0
15 = 00001111
so the first 20 bits are unchanged i.e. 66.66.0.0 /20
The answer given is 66.66.0.0/16 which would include for example 66.66.100.0
But the question is unclear because the CIDR notation is missing. without that this would be a Class A network and the IP addresses would both be on 66.0.0.0/8

Q6
192.168.1.0 - 192.168.120.0 again CIDR is missing so say we assume class C
the first 17 bits are unchanged 120<128
So a good summary would be 192.168.0.0/17
The answer given 192.168.0.0/25 which is only 192.168.0.0 - 192.168.0.127

Q2 the question gives two /13 networks. the answer /16 how can that be a summary.
172.144.0.0/12 I think works.

I could go on