Answer:
Juan's expression is not correct because 1 3/8 equals 11/8 and John used 12/8

Explanation:
we know that
To find out how many 1/4 cup servings are in 1 3/8 cups of juice, divide 1 3/8 cups of juice by 1/4 cup servings
so

but first
Convert mixed number to an improper fraction

substitute in the expression above

Convert to mixed number

Juan's expression is not correct because 1 3/8 equals 11/8 and John used 12/8