Two squares of this net are blank, marked $x$ and $y$; the letters missing from them are D and L. The folded cube is shown on the left. Which letter belongs in square $x$?

In the row $x$ G K $y$ the squares one apart are opposite: $x$ is opposite K, and G is opposite $y$. The cube shows G and D side by side, so D cannot be opposite G, which means D is not in $y$. So D goes in $x$ and L in $y$.