The answer is 15 because if you look at the number if books, it goes by 2. If you look at the prices, it goes by 15. What it is mainly asking for is what the number goes by. Therefore the correct answer is 15.
To convert the amount of milk from deciliters to liters we proceed as follows: 1 liter = 10 deciliters therefore the amount of liters used in making the cake will be found as follows: 5.25/10×1=0.525 liters