odds for a double down or split

does anyone know the odds of winning if you double down on a 9 vs. 3456
10 vs. 23456789 and A vs. 2345678910
im just trying to see if im betting a big hand which situations are the best to just go ahead and do it

also if you could tell me the best hands to split vs. ect... or if anyone just knows a website i could go to.
thanks