Answer:
[tex]6\:\text{cups}[/tex]
Step-by-step explanation:
Since the proportion is maintained, we can set up the following proportion:
[tex]\frac{2/3}{1}=\frac{x}{9}[/tex], where [tex]x[/tex] is the amount of glitter, in cups, Mindy will use to make 9 cups of glittery paint.
Cross-multiply to get:
[tex]1x=9\cdot \frac{2}{3},\\x=9\cdot \frac{2}{3}=\boxed{6\:\text{cups}}[/tex]