Structure of Arguments

This topic, I must say was by far the most difficult topic to understand for me. Please bear with me, if I am travelling down a different path. It took me a while to figure out what part went where, but I can definitely see that this exercise helped me break down arguments and pick out key claims, when I finally understood it.
For the exercises on the Structure of Arguments, I chose to analyze #3.
“Las Vegas has too many people. (1) There’s not enough water in the desert to support more than a million people. (2) And the infrastructure of the city can’t handle more than a million (3): The streets are overcrowded (4), and traffic is always congested (5); the schools are overcrowded (6), and new ones can’t be built fast enough (7). We should stop migration to the city by tough zoning laws in the city and county. (8)”
Argument: yes
Conclusion: We should stop migration to the city by tough zoning laws in the city and county.
Additional Premises Needed? a) If the city’s infrastructure can’t support 1 million people, then there isn’t enough water to support 1 million people. b) Vegas streets are overcrowded and traffic is always congested, schools are overcrowded and new ones aren’t readily available. Therefore Vegas has too many people and we should stop migration to the city by tough zoning laws in the city and county.
Identify any subarguments: 2, 4, 5, and 6 are all independent claims that support 1. Then 1 supports 8.