Out of 10 consonants and 4 vowels, words with 6 consonants and 3 vowels are formed. The number of such words is

The number of ways of choosing 6 consonants out of 10 is ${ }^{10}{C}_6$ and 3 vowels out of 4 in ${ }^4{C}_3$.

 Thus number of such words is $\left({ }^{10}{C}_4\right)\left({ }^4{C}_3\right)\left({ }^9{P}_9\right)=\frac{7}{11}(12!)$