Answer
Theoretical yield: $9.37\ g$
Percent yield: $92.27\%$
Work Step by Step
Number of moles of $CH_3SH$:
$10.0\ g\div 48.11\ g/mol=0.208\ mol$
Theoretical yield:
$0.208\ mol \times 1_{CH_3COSCH_3}/2_{CH_3SH}\times 90.14\ g/mol=9.37\ g$
Percent yield: $8.65/9.37\times100\%=92.37\%$