Proportionality A statement describing the relationship between the variables $x, y,$ and $z$ is given. (a) Express the statement as an equation of proportionality. (b) If $x$ is tripled and $y$ is doubled, by what factor does $z$ change? (See Example $3 . )$
$$z \text { is inversely proportional to the square of } x \text { and the cube of } y$$