i need explanation how they solved this one the answer is provided:

Question

finding the number o fdistinguishable permutations.

(15!)/(4!3!612!) = 6, 306,300

Answer 1

I can assure you it is wrong. The denominator with the factor 612! is much greater than the numerator, therefore, the value as written should be less than one. Something is greatly wrong.

Answer 2

yes instead of being 612! needs to be 6!2!

Answer 3

6(x+1)=12(x-3)