do/end or braces after a method. |x| is the block argument.

Goal

Each city, then map to uppercase.

["Nairobi", "Kisumu"].each { |c| puts c }

units = [12, 8, 5]
units.each do |n|
  puts n * 40
end

cities = ["Nairobi", "Mombasa"].map { |c| c.upcase }
puts cities.inspect

puts [12, 8, 5].select { |n| n >= 8 }.inspect