Comparing glass sizes after pouring water

Glass one is three-quarters full of water and glass two is empty. All of the water from glass one is tipped into glass two, which then turns out to be two-thirds full. What is the capacity of glass one as a fraction of the capacity of glass two?

$8/9$. If the capacities are $x$ and $y$, the same water satisfies $\tfrac34x=\tfrac23y$, so $x/y=\tfrac{2/3}{3/4}=\tfrac89$.