How to factor completely this? please help?

a^3 - b^3 = (a - b)(a^2 + ab + b^2)

27 - (m + 2n)^3
= 3^3 - (m + 2n)^3
= [3 - (m + 2n)][3^2 + 3(m - 2n) + (m + 2n)^2]
= [3 - m - 2n][9 + 3m - 6n + m^2 + 4mn + 4n^2]
= [-m - 2n + 3][m^2 + 3m + 4mn + 4n^2 - 6n + 9]

Answer:

-m^3 - 6m^2n - 12mn^2 - 8n^3 + 27

27-m^3+4m^2n+4mn^2+2nm^2+8mn^2+8n^3

[3 -(m+2n)][9 +(m^2+4n^2+4mn)+3m+6n]

dear, you have to use the formula that
a^3 - b^3 = (a - b)(a^2 +ab + b^2)