product.rb

numbers = []
puts 'Give us first number:'
numbers << gets.strip
puts 'Give us second number:'
numbers << gets.strip

def get_number(str)
  number = 0
  str.split('').reverse.each_with_index do |str, index|
    b = str.bytes.first
    number += ((b - 48) * 10 ** index)
  end
  number
end

result = get_number(numbers[0]) + get_number(numbers[1])
puts "result #{result}"