Simplifying exponential expressions, can you please confirm my solutions are correct?

A.

(3x^4y^5z^7)^5 / (-3x^3yz^4)^7

= -1^5-7x^20-21y^18z^7 = -1^-2x^-1y^18z^7

Solution I arrived at:

y^18z^7/ x

B.[x^(a+b)]^(a-b) / [x^(a-2b)]^(a+2b)

Solution:

= 1^(3b^2)

Thanks in advance.

Sincerely,

Raymond MacNeil