Which subnet is host 180.100.1.220 /27 in?

We have skipped a subnet.  The principles are exactly the same.  Remember to use the Subnetting Secrets Chart© to save time and to insure that your answer is correct.  You are hitting the fourth octet in this example so you would just tick down three places (because you can’t fit in the 8 bits on the third octet on the chart.