We know that 2 cups of flour makes 20 biscuits.
2/2=1
20/2=10
To make 10 biscuits, you need 1 cup of flour. I know that because I cut the amount of flour in half because half of 20=10.
10 x 3 = 30
Because 10 times 3 is equal to 30, you can multiply the amount of flour by three to find out how much flour you will need for 30 biscuits.
1 x 3 = 3
You will need 3 cups of flour to make 30 biscuits.
The correct answer is B.
Hope this helped :)! Tell me if you want me to explain it in a different way.