module Adder
  def add(operand_one, operand_two)
    return operand_one + operand_two
  end
end

module Subtracter
  def subtract(operand_one, operand_two)
    return operand_one - operand_two
  end
end

class Calculator
  include Adder
  include Subtracter
end

calculator = Calculator.new()

puts "2 + 3 = " + calculator.add(2, 3).to_s

