If [tex]m[/tex] is the mass of the envelope and [tex]b[/tex] the mass of one bookmark, then
[tex]\begin{cases}m+96b=1467\\m+49b=762\end{cases}[/tex]
We have
[tex](m+96b)-(m+49b)=1467-762\implies47b=705\implies b=15[/tex]
Then
[tex]m+96\cdot15=1467\implies m+1440=1467\implies m=27[/tex]
so the envelope has a mass of 27 grams.
