You may use a calculator to complete this test. if 1 egg and 1/3 cup of oil are needed for each bag of brownie mix, how many bags of brownie mix do you need if you want to use up all 3 eggs and 1 cup of oil?
If you go from using 1 egg to 3 eggs, you are multiplying the amount you use by 3. If you multiply 1/3 by 3, you get 1 cup of oil. Apply that to your 1 bag of brownie mix, and you get a total of 3 brownie mix bags.