If $2^{x+1}=4^{x-7}$ and $8^{3y}=16^{-y+13}$, what is the value of $x+y$?
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
If $2^{x+1}=4^{x-7}$ and $8^{3y}=16^{-y+13}$, what is the value of $x+y$?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
19
If $2^{x+1}=4^{x-7}$ and $8^{3y}=16^{-y+13}$, what is the value of $x+y$?
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