Write the reaction

Methylation of benzene gives toluene: $\mathrm{C_6H_6 \rightarrow C_7H_8}$

The mole ratio is 1 : 1.

Calculate moles of benzene used

Molar mass of benzene, $\mathrm{C_6H_6}$: $6\times 12 + 6\times 1 = 78\,\text{g mol}^{-1}$

Moles of benzene: $n = \frac{10}{78}\,\text{mol}$

Calculate theoretical mass of toluene

Molar mass of toluene, $\mathrm{C_7H_8}$: $7\times 12 + 8\times 1 = 92\,\text{g mol}^{-1}$

Since the ratio is $1:1$, theoretical moles of toluene: $\frac{10}{78}\,\text{mol}$

Therefore, theoretical mass of toluene: $\frac{10}{78}\times 92 = 11.79\,\text{g}$

Calculate percentage yield

Actual mass of toluene obtained = $9.2\,\text{g}$

$\%\text{yield} = \frac{\text{actual yield}}{\text{theoretical yield}}\times 100$

$\%\text{yield} = \frac{9.2}{11.79}\times 100 \approx 78.03\%$

Nearest integer

$\boxed{78}$

Comparison with stored answer

The derived answer is $78$, which matches the stored correct answer.