What is the sum of all values of $x$ for which the expression $\frac{x-3}{x^2-10x+16}$ is undefined?
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
What is the sum of all values of $x$ for which the expression $\frac{x-3}{x^2-10x+16}$ is undefined?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
10
What is the sum of all values of $x$ for which the expression $\frac{x-3}{x^2-10x+16}$ is undefined?
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