Hi there --
If a plane can climb 2,400 feet per minute, it will need 25 minutes to reach 60,000 feet. // By dividing 60,000 (the needed feet) by 2,400 (the amount of feet the plane can climb per/min) you get 25 (the amount of mins needed to climb 60,000 feet)
Hope this helps! Have a great day! :)