José bought for notebooks more than twice of a number he has now 12 notebooks what is the number

Which of the following is most likely the next step in the series? a3z, b6y, c9x, d12w, е15v, f18u

What is the multiple zero and multiplicity of f(x) = (x ? 3)(x ? 3)(x + 5)? multiple zero is 3; multiplicity is 2 multiple zero is 5; multiplicity is 1 multiple zero is ? 5; multiplicity is 1 multiple zero is ? 3; multiplicity is 2

(60 points) explain this in detail