I need help on this one question lol

Segment xz is bisected by point y. if xy = 12x, and the measure of xz = 18x – 6, solve for x

Alina fully simplifies this polynomial and then writes it in standard form. xy2 – 2x2y + 3y3 – 6x2y + 4xy2 if alina wrote the last term as 3y3, which must be the first term of her polynomial in standard form? xy2 5xy2 –8x2y –2x2y

Hi i’m not sure how to do question 20 if u could explain how to do it that’d b great