+ = 1
========>
2*(n+3) + 2n = n*(n+3)
2n + 6 + 2n = n^2 + 3n
n^2 - n - 6 = 0
(n-3)*(n+2) = 0.
The roots are n= 3 and n= -2.
Since you are looking for positive n, only the root n= 3 is the solution.
Answer. Positive integer n = 3.
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In future, when there are formulas in your post, use parentheses to separate different parts and make clear which part of the formula
is the numerator and which part is the denominator. Otherwise your formulas are ambiguous and/or unreadable.