A recipe for potato salad calls for one teaspoon of vinegar for every 2 teaspoons of mayonnaise. How many teaspoons of vinegar are needed for 16 teaspoons of mayonnaise

8 teaspoons, you make the ratio 1:2. then fill it in as x:16, for every 1 teaspoon of vinager you have 2 of mayo. so you'd need to make sure than x, would make 1:2 true. 8:16 is the solution because reduced it is 1:2.