One-quarter of a bread recipe calls for 2/3 cup of bread flour. How many cups are needed per recipe?

We know that 1/4 of a recipe calls for 2/3 cup of bread flour. So lets make this proportion (2/3) cup / (1/4) recipe, or if we simplify, 8 cup / 3 recipe. This is actually already the answer! If we need 8 cups for 3 recipes, just divide both by 3, and we get 8/3 cups for 1 recipe.

Alternatively you can think of the problem this way:

We need 2/3 cup for 1/4 recipe. 4 times 1/4 recipe is 1 recipe. Thus, 4 * 2/3 = 8/3.