It should be \(81+256=337.\) First, change the fourth root into \(\frac{1}{4}.\)
Now, without words:
\(x^{\frac{1}{4}}=\frac{12}{7-x^{\frac{1}{4}}}\)
\(x^{\frac{1}{4}}\left(7-x^{\frac{1}{4}}\right)=\frac{12}{7-x^{\frac{1}{4}}}\left(7-x^{\frac{1}{4}}\right)\)
\(x^{\frac{1}{4}}\left(7-x^{\frac{1}{4}}\right)=12\)
Expand, \(7x^{\frac{1}{4}}-\sqrt{x}=12\)
\(7x^{\frac{1}{4}}-\left(x^{\frac{1}{4}}\right)^2=12\)
Plug variables instead of \(x^\frac{1}{4}\)
to get \(x=81,\:x=256\)
Thus, te answer is \(81+256=\boxed{337}.\)
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