Is this a fraction problem or a adding problem math ego practice

It's not exactly either, well maybe repeated addition, since I would multiply 56 bottles by 20 ounces to find the total amount of water, then I would divide by 16 ounces to see how many bottles it would take to match that amount of water.

Set up as an equation this way:

16x = 56 (20)

16x = 1120

x = 70

Therefore, you would need 70 16-ounce bottles to hold the same total amount of water as 56 20-ounce bottles.