Step 1: Use the formula for percentage yield. $$ \text{Percentage yield} = \frac{\text{Actual yield}}{\text{Theoretical yield}} \times 100 $$ From the image, the actual yield is 33 and the theoretical yield is 42. Step 2: Substitute the values into the formula. $$ \text{Percentage yield} = \frac{33}{42} \times 100 $$ Step 3: Perform the division. $$ \frac{33}{42} \approx 0.7857142857 $$ Step 4: Multiply by 100 to get the percentage. $$ 0.7857142857 \times 100 \approx 78.57142857\% $$ Step 5: Round the answer to the nearest whole number, as indicated by the final step in your work ($79\%$). The first decimal place is 5, so we round up the whole number. $$ 78.57142857\% \approx 79\% $$ The percentage yield is: $$ \boxed{79\%} $$