You want to find out how many cups of flour Jaylin needs to make 30 biscuits.
We currently know 2 cups of flour makes 20 biscuits.
We can halve the recipe down to make it simplier - simply divide all ingredients by 2 to halve it.
1 cup of flour = 10 biscuits
Since 1 cup of flour equals 10 biscuits, and 2 cups of flour equals 20 biscuits, we can safely say 3 cups of flour equals 30 biscuits.