To add 2/3 + 3/5 using 15 soup cans, what common denominator would be easiest?

How would you show each fraction using the 15 soup cans to add 2/3 + 3/5?

How many cans would you have when using the 15 soup cans to add 2/3 + 3/5?

How would you know whether you had more or less than 1 whole?