How many 4-digit numbers can be created such that the only digits that can be used are 3, 6 and 9, a specific digit can occur at most three times in the number, and the number must be divisible by 9?

Ithink i know it but i want to be sure so can you me out ?

Ineed with the quizzes in apex mathematics ii

Answer asap! show all work! find the number of complex roots, the possible number of real roots and the possible rational roots of the polynomial function. then, solve for all roots. x^3 + 2x^2 + 3x + 6 = 0