Help!

I have been searching for the phrase "five will get you ten" and can't find it. I know it is used in the song "Mack the Knife." Does anyone know what it means/it's origin?
Thanks!
Lesley

It's betting parlance. Betting 5 (dollars, pounds, matchsticks) will get you (win for you) 10 (dollars, etc.) In other words, even odds.