To simplify each expression:

30x^2y + 11y
This expression cannot be simplified further because the terms are not like terms.

5x^2y - xy
This can be simplified by combining the like terms:
= 5x^2y - xy
= (5x^2 - 1) * y

27m^5 - 3m^2
This can be simplified by combining the like terms:
= 27m^5 - 3m^2

15x^2 - y^4 - 25x^3y^3 + 5x^2y
This expression can be simplified by combining the like terms:
= 20x^2 - y^4 - 25x^3y^3