What is that formula doing?! Why do you do 0 + 60? Why not just start with 60?

Anyway what you want to do is this...

50/(odds-1)

Where you want to make $50 profit (i.e not including your stake). So if it was a 1.50 horse you'd stake $100 (50/0.5). A $10 horse and you'd only need to stake $5.56.