Hello!
To solve this, I would convert to improper fractions. This is done by multiplying the integer with the denominator and adding it to the numerator.
9 3/8: 9*8+3=72+3=75
4 3/8: 4*8+3=32+3=35
So the improper fractions therefore are 75/8 and 35/8.
Now to see what fractions of each other they are, you can just divide the numerators because the denominators cancel each other out.
35/75 = 7/15
So your answer would be 7/15, or B.
Hope this helped!