Let $z \in C$ with $\text{Im}(z) = 10$ and it satisfies $\frac{2z-n}{2z+n} = 2i - 1$, $i = \sqrt{-1}$ for some natural number $n$, then}
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When solving equations involving complex numbers, always express the complex number in the form $x+iy$ and then equate the real and imaginary parts on both sides of the equation. Remember that $i^2 = -1$.