2019 Mock AMC 10B Problems/Problem 7

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Solution by excruciating: Subtracting $n$ from both sides gives \[x^2-8x+(96-n^2)=0.\] For any quadratic $ax^2+bx+c$, the sum of the roots is $-\frac{b}{a}.$ So, the sum of the roots is $-\frac{(-8)}{1} = \boxed{(A) 8}$. Note that whatever $n$ is does not affect the sum of the roots.