It is given that Henry has 52/9 ounces of dark chocolate.
Each gravestone requires 2/9 ounces of dark chocolate.
Hence the number of gravstones that can be made is given by:
[tex]\begin{gathered} \frac{\frac{52}{9}}{\frac{2}{9}}=\frac{52}{9}\times\frac{9}{2} \\ =\frac{52}{2} \\ =26 \end{gathered}[/tex]Hence the number of gravestones possible is 26.