If a plan can travel 470 miles per hour with the wind and 430 miles per hour against the wind find the speed of the wind and the speed of the plane in still air.

470-390=80
80/2=40
The wind is 40 mph
What does find the speed of the wind in still air mean? The wind is not still air!

Do you mean find the speed of the wind or find the speed of the plane in still air? Try reading your post before clicking submit.
470-40=430
390+40=430
The plane in still air goes 430 mph

470 subtract 430 would be 40 miles per hour.