Hi Gtvr, thank you for helping.
i just changed the ips on the computers, the dsl modem that is also a rauter i did no touch. the model is Dlink dsl 540 b
the set up now that is working is:
dsl modem ip address 192.168.254254
computers ip address is 192.168.254.1 to 21
computers gateway is 192.168.254.254
now what i was looking for is a way to divide this network
into 3 netwoks with 7 computers in each one, and istill be able to access the internet router.