well, first off, hmmm let's find their slopes in the first place

now, to get the equation of any straight line, we simply need two points off of it, let's use those two in the picture below for BrandY

to get the equation of any straight line, we simply need two points off of it, let's use those two in the picture above for BrandZ
![(\stackrel{x_1}{0}~,~\stackrel{y_1}{3})\qquad (\stackrel{x_2}{4}~,~\stackrel{y_2}{9}) ~\hfill \stackrel{slope}{m}\implies \cfrac{\stackrel{\textit{\large rise}} {\stackrel{y_2}{9}-\stackrel{y1}{3}}}{\underset{\textit{\large run}} {\underset{x_2}{4}-\underset{x_1}{0}}} \implies \cfrac{ 6 }{ 4 } \implies {\Large \begin{array}{llll} \cfrac{3 }{ 2 }=Z \end{array}} \\\\[-0.35em] ~\dotfill\\\\ ~\hfill \stackrel{X}{2} ~~ > ~~ \stackrel{Y}{1}\hspace{5em}\stackrel{X}{2}~~ > ~~ \stackrel{Z}{(3)/(2)}~\hfill](https://img.qammunity.org/2024/formulas/mathematics/high-school/dz19t6pcdcyv8igffcxr4szgtqta05lvfv.png)