John can walk 6 dogs in 3 hours. Susie can walk 7 dogs in 2.5 hours. How long would it take them to
walk 15 dogs together?

It would take them 6.5 hours to walk 15 dogs together.

Step-by-step explanation:

John can walk 2 dogs in 1 hour.

If you multiply that by 3, he can walk 6 dogs in 3 hours.

So that means he can walk 8 dogs in 4 hours.

Susie can walk 7 dogs in 2.5 hours.

Meaning that if you add 8 dogs plus 7 dogs, you get 15 dogs.

Meaning that if you add 4 hours plus 2.5 hours, you get 6.5 hours.

That being said, they can both walk 15 dogs TOGETHER in 6.5 hours.