phone_number.rb

class Phone
  attr_reader :number

  def initialize(input)
    @number = validate_phone(input)
  end

  def area_code
    number[0..2]
  end

  def to_s
    "(#{area_code}) #{number[3..5]}-#{number[6..10]}"
  end

  private

  def validate_phone(number)
    phone = clean(number)

    if phone.length == 10
      phone
    elsif phone.length == 11 && phone[0] == "1"
      phone[1..10]
    else
      invalid_phone
    end
  end

  def clean(phone)
    phone.gsub(/\D/, '')
  end

  def invalid_phone
    "0000000000"
  end
end

robot_name.rb

class Robot
  attr_reader :name

  def initialize
    generate_name
  end

  def reset
    generate_name
  end

  private

  def generate_name
    @name = ""
    2.times { @name << letter }
    3.times { @name << digit  }
  end

  def letter
    rand(65..90)
  end

  def digit
    rand(0..9).to_s
  end
end