calc.rb

@number = 0 
print "How much should we add:"
 @number + gets.chomp.to_i
  puts "> #{@number}"
print "How much should we subtract:"
  @number - gets.chomp.to_i
  puts "> #{@number}"
print "How much should we multiply:"
  @number = gets.chomp.to_i * @number
  puts "> #{@number}"
print "How much should we divide:"
    @number = @number / gets.chomp.to_i
    puts "> #{@number}"
print "Would you like to add again?"
  puts answer = gets.chomp
  if answer == "yes"
    calculator.rb
  else
    return
  end

calculator.rb

class Calculator
  def initialize
    @number = 0 
  end

  def add
    print "How much should we add:"
    n = gets.chomp.to_i
    @number = n + @number
    puts "> #{@number}"
  end

  def subtract
    print "How much should we subtract:"
    n = gets.chomp.to_i
    @number = @number - n
    puts "> #{@number}"
  end

  def multiply
    print "How much should we multiply:"
    n = gets.chomp.to_i
    @number = n * @number
    puts "> #{@number}"
  end

  def divide 
    print "How much should we divide:"
    n = gets.chomp.to_i
    @number = @number / n
    puts "> #{@number}"
  end
  
  def repeat
    print "Would you like to add again?"
    answer = gets.chomp
    if answer == "yes"
      run_file
    else
      return
    end
  end

  def run_file
    add
    subtract
    multiply
    divide
    repeat
  end
end

calc = Calculator.new
calc.run_file