²/₃ , ⁴/₇ , ? , ¹¹/₂₁ , ¹⁶/₃₁

Explanation:-

The sequence in the numerators is + 2, + 3, + 4, + 5 and that in the denominators is + 4, + 6, + 8, + 10
So, the numerator of the missing fraction should be (4 + 3)i.e., 7 and the denominator should be (7 + 6)i.e., 13. Thus, the missing term is ⁷/₁₃ .