Answer:
3 -n/2 ≤ 5
Explanation:
You want a math expression that means "half a number less than 3 is at most 5."
Translation
We can let "n" represent "a number." Then "half a number" is (1/2)n or n/2.
That amount "less than 3" means it is subtracted from 3:
3 -n/2 . . . . . . half a number less than 3
The wording "is at most" means "is less than or equal to." In symbols, the words mean ...
3 -n/2 ≤ 5
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Additional comment
Often 'x' is used to represent an unknown quantity. We like 'n' for "a number" because it is mnemonic, and because the numbers of interest are often integers or natural numbers from the set represented by ℕ.
English expressions of math relations are often ambiguous. In this case, we're not completely sure that the intention is not "half (a number less than 3)", which would be (3 -n)/2. Usually, we fall back on the Order of Operations, which requires that multiplication be done before addition. That is "half a number" must be computed before "less than 3" is evaluated, hence 3 -n/2.