Answer:
[tex]\frac{2}{7}[/tex]
Step-by-step explanation:
We have,
The recipe need [tex]\frac{2}{5}[/tex] cups of flour.
Also, the chef is making the amount which is [tex]\frac{5}{7}[/tex] of the recipe.
Thus, the total amount of the flour required will be,
[tex]\frac{2}{5}\times \frac{5}{7}[/tex] = [tex]\frac{2}{7}[/tex] cups.
Hence, the chef should use [tex]\frac{2}{7}[/tex] cups of flour.