Đáp án: a) x = $\frac{-37}{56}$
b) x = 0,4
c) x = $\frac{-1}{15}$
Giải thích các bước giải:
a) $\frac{2}{7}$ + x = $\frac{-3}{8}$
=> x= $\frac{-3}{8}$ - $\frac{2}{7}$ = $\frac{-21}{56}$ - $\frac{16}{56}$ = $\frac{-37}{56}$
b) $\frac{7}{15}$ + ($\frac{5}{6}$ - x) = $\frac{9}{10}$
=> $\frac{5}{6}$ - x = $\frac{9}{10}$ - $\frac{7}{15}$
=> x= $\frac{5}{6}$ -($\frac{9}{10}$ - $\frac{7}{15}$ )
=> x= $\frac{5}{6}$ - $\frac{9}{10}$ + $\frac{7}{15}$
=> x= $\frac{25}{30}$ - $\frac{27}{30}$ + $\frac{14}{30}$
=> x= $\frac{12}{30}$
=> x= $\frac{2}{5}$ = 0,4
c) x - $\frac{1}{3}$ = -$\frac{2}{5}$
=> x= -$\frac{2}{5}$ + $\frac{1}{3}$
=> x= $\frac{-6}{15}$ + $\frac{5}{15}$
=> x= $\frac{-1}{15}$
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