In this symbolism question, you not only have to apply the rule to the question, but also to all of the answer choices. Start with the question.

Since 7 is odd, ]7[ = 2(7) + 1 = 15.

Since 4 is even, ]4[ = 4/2 + 1 = 3.

The product of 15 and 3 is 45, so we're looking for a choice equal to 45. Consider each one:
(A) ]22[ = 22/2 + 1 = 12
(B) ]44[ = 44/2 + 1 = 23
(C) ]45[ = 2(45) + 1 = 91
(D) ]88[ = 88/2 + 1 = 45
(E) ]90[ = 90/2 + 1 = 46

(D) is correct.