Question

if puppy food can be softened with 3 parts dog food with one part water how much dog food can be softened with 16 cups water

Answer 1

You need to multiply. 3 x 16. which equals to 48 dog food

Answer 2

Look at it this way: 
For every one cup of water you can soften 3 cups of puppy food you have 16 cups of water you can soften 16*3
16*3=48
Your answer is 48.