Use special products for this:
Cube of a trinomial:
(a-b)³ = a³ - 3a²b + 3ab² - b³
Just substitute and simplify, and let:
a = 3x
b = 6y
So we will have:
(a-b)³ = a³ - 3a²b + 3ab² - b³
(3x - 6y)³ = (3x)³ - 3(3x)²(6y) + 3(3x)(6y)² - (6y)³
= 27x³ - 3(9x²)(6y) + 3(3x)(36y²) - 216y³
= 27x³ - 162x²y + 324xy² - 216y³ ......ANSWER
