Tìm x biết:
a) \(x = \frac{1}{4} + \frac{2}{{13}}\)
b) \(\frac{x}{3} = \frac{2}{3} + \frac{{ - 1}}{7}\)
Câu a
\(\begin{array}{l}
x = \frac{1}{4} + \frac{2}{{13}}\\
= \frac{{13}}{{52}} + \frac{8}{{52}} = \frac{{21}}{{52}}
\end{array}\)
Câu b
\(\begin{array}{l}
\frac{x}{3} = \frac{2}{3} + \frac{{ - 1}}{7}\\
= \frac{{14}}{{21}} + \frac{{ - 3}}{{21}} = \frac{{11}}{{21}}
\end{array}\)
Suy ra \(x = \frac{{11}}{{21}}.3 = \frac{{11}}{7}\)
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