database variables calculation in ruby

[monica23]

Hi everybody, in my database, am trying to print the value of total and then add it to the price,
i was able to fetch the value of total but when i tried to add it to to price so as to get value of sum in this line
of code

    sum = price + %s, row[0]  
    puts "sum"

nothing happens. where am i supposed to perform the operations, is outside the loop. below is the code, any help please

    #!/Ruby19/bin/ruby 
    require 'cgi'

    cgi = CGI.new
    puts cgi.header

    require "dbi"



     price = '100'
    begin
       # connect to the MySQL server
         conn = DBI.connect("DBI:Mysql:db:localhost", 
    	                    "root", "root566")

        rs = con.query("SELECT total from product where product_id = '20'")

       row = stmt.fetch do
          
       end
       puts "<font color=green size=4><b>get total values</b></font><br><br>"

     printf '<b>total:</b> %s<br>', row[0]

     sum = price + %s, row[0]  
    puts "sum"
     
       
             
    rescue Mysql::Error => e
        puts e.errno
        puts e.error
        
    ensure
        con.close if con
    end