((13)³+7³)/((13)²+7²-?)=20 · ABC26GN1215
Subject: General Aptitude · Chapter: Simplification
$\frac{(13)^{3}+7^{3}}{(13)^{2}+7^{2}-?}=20$
(a)6
(b)20
(c)91
(d)None of these
Answer
Explanation
Let $\frac{13^{3}+7^{3}}{13^{2}+7^{2}-x}=20$. Then, $\frac{13^{3}+7^{3}}{13+7}=13^{2}+7^{2}-x$ $$\begin{aligned} & \Leftrightarrow 13^{2}+7^{2}-13 \times 7=13^{2}+7^{2}-x \\ & \Leftrightarrow x=13 \times 7=91 . \end{aligned}$$
Explanation as extracted from the printed page; notation may be imperfect.
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