To determine who spent more time writing per problem, we need to calculate the unit rate (minutes per problem) for both Sonia and Maryna based on the data provided.
**For Sonia:**
1. For 6 problems:
\[\frac{120 \text{ minutes}}{6 \text{ problems}} = 20 \text{ minutes/problem}\]
2. For 18 problems:
\[\frac{360 \text{ minutes}}{18 \text{ problems}} = 20 \text{ minutes/problem}\]
3. For 25 problems:
\[\frac{500 \text{ minutes}}{25 \text{ problems}} = 20 \text{ minutes/problem}\]
4. For 60 problems:
\[\frac{1200 \text{ minutes}}{60 \text{ problems}} = 20 \text{ minutes/problem}\]
**Average for Sonia:**
Sonia consistently spent 20 minutes per problem.
---
**For Maryna:**
1. For 8 problems:
\[\frac{200 \text{ minutes}}{8 \text{ problems}} = 25 \text{ minutes/problem}\]
2. For 15 problems:
\[\frac{375 \text{ minutes}}{15 \text{ problems}} = 25 \text{ minutes/problem}\]
3. For 20 problems:
\[\frac{500 \text{ minutes}}{20 \text{ problems}} = 25 \text{ minutes/problem}\]
4. For 50 problems:
\[\frac{1250 \text{ minutes}}{50 \text{ problems}} = 25 \text{ minutes/problem}\]
**Average for Maryna:**
Maryna consistently spent 25 minutes per problem.
---
**Comparison of writing times per problem:**
- Sonia: 20 minutes per problem
- Maryna: 25 minutes per problem
Therefore, **Maryna spent more time writing per problem at the unit rate of 25 minutes per problem.**