Below I will translate from decimal to binary just for the second octet
The theory says the IP range is: 172.16.0.0/12 with addresses ranging between 172.16.0.0-172.31.255.2555
that translates to:
172.00001110.0.0 with mask on the next line
255.11110000.0.0
So the base address for this range is:
172.00000000.0.0 which is 172.0.0.0 and not 172.16.0.0
where is the mistake here ? ☺