def string_evaluation(string)
  values_mult = string.scan(/\d+[*]\d+/)

  values_mult.each do |math|
    i, j = math.scan(/\d+/)
    string = string.gsub! math, (i.to_i*j.to_i).to_s
  end

  if !string.scan(/\d+[*]\d+/).empty?
    string_evaluation(string)
  else
    values_sum = string.scan(/\d+/)
    sum = values_sum.map(&:to_i).reduce(:+)
    puts sum
  end
end