7 cups and 3 fl oz - 3 cups and 4 fl oz
1 cup = 8 oz.
7 3/8cups - 3 4/8cups = 59/8 - 28/8 = 31/8 = 3 7/8 cups.
he is right
https://www.google.com/search?q=subtracting+cups+and+ounces&oq=subtracting+cups+and+ounces&aqs=chrome..69i57.6489j0j7&sourceid=chrome&ie=UTF-8
What will your result be?