1) is not equivalent if you distribute the 9 you get 36g-27x+9 which is wrong because it has -27x instead of +27x
2) I’m gonna assume that the number after the variable is the power ( next time use the symbol ^) but in this case it will be
not equivalent because you will have 3x-18 which is not 3x^3-18 because you do not gain a power
3) not equivalent because you will have added all like terms together and have gotten 6x^5+2z+17. This is not equivalent because you one equation has a +2z and the other has -2z
