Help with math problem please?

Question

Directions simplipy each by doing the indicated opertions and combing like terms. Theirs no differnt types of problems im confuesed wtih, please show me how to do it, i want to learn so i can do rest of problems

here is one example of a similiar problem im trying to figure out how to solve -3xy cubed(x-2y)

heres another

(-3x squared y cubedz)cubed

Answer 1

in the first question, is just the y cubed?  or is the entire first term cubed?  i'll assume it's the first case, but please let me know if i'm wrong.

Problem 1: x^a * x^b = x^(a+b)

-3 * x * y^3 * (x - 2*y)

= (-3*x * y^3)*x - (-3 * x * y^3)*(-2*y)

= (-3 * x*x * y^3) + (6 * x * y*y^3)

= (-3 * x^2 * y^3) + (6 * x * y^4)

Problem 2: (x^a)^b = x^(a*b)

(-3 * x^2 * y^3 * z)^3

= (-3)^3 * (x^2)^3 * (y^3)^3 * z^3

= -27 * x^6 * y^9 * z^3