Phil drives 5 hours at an average speed of 30 miles per hour. then she drives 3 hours at a speed of 40 miles per hour. what is her average speed for the whole trip?

Megan and desmond each add the same amount of water to their aquarium megan makes 5 ml of chemical solution with every gallon of water for her aquarium desmond mixed 8 ml of chemical solution for every 2 gallon of the water for his aquarium.