rubymonk exercise

def add(*numbers)
  numbers.sum
end

def subtract(number, *more_numbers)
  more_numbers.each do |i|
    number -= i
  end
  number
end

def calculate(number, other_number, options = {})
  if options.is_a?(Hash) && options[:subtract]
    subtract(number, other_number)
  else add(number, other_number)
  end
end