Ruth is making lemonade. For 1 cup of water she uses 3 lemons, for 2 cups 6 lemons, etc. if this pattern continues, how many lemons will she need for 10 cups of water

She'll need 30 lemons for 10 cups of water. Just multiply 3 by 10, or you can add 3 to every cup of water.

My answer is short, but hopefully I helped.