Roll the dice three times at a time and find the event probability with exactly 9 points? Thank you~

Three dice appear 6*6*6=2 16. If the sum is 9, there is 126(3! =6 kinds) 135(3! =6 species) 144(3 species) 225(3 species) 234(3! =6 species) 333( 1 species) * * 6+6+3+6+ 1 = 25 species with a probability of 25/2 16.