Answer:
It takes 3.5 cups of pancake mix and 2.625 cups of water to make 21 pancakes.
Step-by-step explain
First divide each by 6 to figure out how much mix and water it takes to make one pancake
1/6 mix + .125 cups water = 1 pancake
Multiple each by 21 to know how much mix and water it takes to make 21 pancakes
3.5 mix + 2.625 water = 21 pancakes