A pancake mix requires 2 cups of flour for every 10 pancakes
meaning for a cup of flour, we will have 5 pancakes
1flour/5pancake (1 flour for 5 pancakes)
The question asks for every pancake, how many cups of flour do we need, hence we can divide by 5 as such
(1/5 flour)/(5/5 pancake) = 1/5 flour/pancake
meaning we need 1/5 cup of flour for a pancake