To determine who spends less time on homework per night, we can calculate the average number of hours spent on homework per day for both Marco and Maribella.
For Marco:
- For 3 days: \( \frac{3.25 \text{ hours}}{3 \text{ days}} = 1.0833 \text{ hours per day} \)
- For 9 days: \( \frac{9.75 \text{ hours}}{9 \text{ days}} = 1.0833 \text{ hours per day} \)
- For 12 days: \( \frac{13.0 \text{ hours}}{12 \text{ days}} = 1.0833 \text{ hours per day} \)
- For 30 days: \( \frac{32.5 \text{ hours}}{30 \text{ days}} = 1.0833 \text{ hours per day} \)
Average for Marco: 1.0833 hours/day
For Maribella:
- For 4 days: \( \frac{4.2 \text{ hours}}{4 \text{ days}} = 1.05 \text{ hours per day} \)
- For 8 days: \( \frac{8.4 \text{ hours}}{8 \text{ days}} = 1.05 \text{ hours per day} \)
- For 20 days: \( \frac{21.0 \text{ hours}}{20 \text{ days}} = 1.05 \text{ hours per day} \)
- For 28 days: \( \frac{29.4 \text{ hours}}{28 \text{ days}} = 1.05 \text{ hours per day} \)
Average for Maribella: 1.05 hours/day
Conclusion: Marco spends an average of 1.0833 hours per day on homework, while Maribella spends 1.05 hours per day. Therefore, Maribella spends less time on homework per night.
So, the correct statement is: Maribella spends less time on homework per night.