Algebra help

Question

A plane flies 405 miles with the wind and 315 miles against the wind in the same length of time. If the speed of the wind is 20 mph, find the speed of the plane in still air.

Answer 1

https://www.wyzant.com/resources/answers/394275/question_in_lower_description

 

I have solved this problem. It is at that link.

 

Please refrain from posting the same problem twice.

 

Thank you.