The answer is letter A.
The average amount of milk used for an orders of pancakes can be found by taking the total number of cups used for the 10 pancakes and take the answer divided by 10 (the amount of total pancakes)
We have 6 of 1/2 cups, 2 of 1/4 cups and 2 of 3/4 cups
So there are a total of [6•(1/2)]+[2•(1/4)]+[2•3/4]=5 cups for the total of 10 pancakes
Therefore, the average amount of milk used for an order of pancakes is 5/10=1/2 cups.