I need help with this problem​

Two airplanes start at the same place and travel in opposite directions,one at 395 miles per hour and the other at 422 miles per hour. how many hours will it take for the planes to be 2451 miles apart?

Astocks price gained 3% in april and 5% in may and then lost 4% in june and 1% in july during which month did the stocks price change the most

Allen wants to buy a hover board that sells for $249.99 and a helmet that is $36.54. how much change will allen receive if he gives the cashier three $100.00 bills?