Speed of wind is 4.90 miles per hour
Step-by-step explanation:
Let the speed of wind be w.
Alicia’s average speed riding her bike = 12 mph
Speed against wind = 12 - w
Speed with wind = 12 + w
Total distance traveled = 40 miles
Total time taken = 4 hours
Distance to beach is half of the distance traveled which is 20 miles
We have

Speed of wind is 4.90 miles per hour