Zero-based index. push mutates. each walks.

Goal

Puts cities and a pushed Eldoret.

cities = ["Nairobi", "Mombasa", "Kisumu"]
puts cities[0]
puts cities.length

cities = ["Nairobi", "Mombasa"]
cities.push("Kisumu")
puts cities.inspect

cities = ["Nairobi", "Mombasa", "Kisumu", "Nakuru"]
puts cities[0, 2].inspect
puts cities.include?("Eldoret")

units = [12, 8, 5]
puts units.join(", ")