Answer:
Oxygen.
Explanation:
They take in oxygen from the air. This is the process of respiration.
<em />If 100 brownies require 6 eggs, 5 cups of flour, and 2 sticks of butter. Then, 50 brownies should require half of those required to make 100 brownies. Use ratio and proportion to determine the number of eggs needed:
100/50 = 6/x
x = 3<span />