Answer:
10 mph
Step-by-step explanation:
Let x mph be Devontre rate uphill, then x+20 mph its his rate downhill.
1. Time uphill:
2. Time downhill:
3. If it took him 20 minutes (1/3 hour) longer to ride uphill than downhill, then
Solve this equation:
The rate cannot be negative, thus, x=10 mph (rate uphill).
Answer:3