5 chances of Hearts winning the league for every 7 chances of them losing. So, out of 12 chances, they have 5 to win. That's a 42.5% chance of winning the league (5/12ths).
With Rangers likely to drop points for a negative financial event and Hearts looking like they might win outright anyway, it really is like buying money. You can lump on now and then, if things go pear-shaped for Hearts, lay off against them - and still make loadsamoney.