Check the 1st picture below. Let's see if that's true for the 1st one, by substituting the values
[tex]\begin{cases} x = 9\\ y = -3\end{cases} \\\\[-0.35em] ~\dotfill\\\\ y = -x + 6 \implies -3 = -(9)+6\implies -3=-3\qquad \textit{\large \checkmark} \\\\\\ y = \cfrac{2}{3}x-9 \implies -3 = \cfrac{2}{3}(9)-9\implies -3=6-9\implies -3=-3\qquad \textit{\large \checkmark}[/tex]
now let's do the 4th one, Check the 2nd picture below.
[tex]\begin{cases} x = 12\\ y = 18\end{cases} \\\\[-0.35em] ~\dotfill\\\\ y = \cfrac{3}{2}x \implies 18 = \cfrac{3}{2}(12)\implies 18=6\cdot 3\implies 18=18\qquad \textit{\large \checkmark} \\\\\\ y = \cfrac{3}{4}x+9 \implies 18 = \cfrac{3}{4}(12)+9\implies 18 = (3\cdot 3)+9 \\\\\\ 18=9+9\implies 18=18\qquad \textit{\large \checkmark}[/tex]
