Đáp án:
a) $\frac{5}{4}$ -$\frac{1}{2}$ + $\frac{-7}{8}$
= $\frac{5x2}{4x2}$ - $\frac{1x4}{2x4}$ +$\frac{-7}{8}$
=$\frac{10}{8}$- $\frac{4}{8}$+ $\frac{-7}{8}$
= $\frac{-1}{8}$
b)(-$\frac{5}{24}$ + 0,75 + $\frac{7}{12}$ ) : (-2$\frac{1}{8}$)
= (-$\frac{5}{24}$+$\frac{3x6}{4x6}$ + $\frac{7x2}{12x2}$) : $\frac{-15x3}{8x3}$
= (-$\frac{5}{24}$ + $\frac{18}{24}$ + $\frac{14}{24}$) :$\frac{-45}{24}$
= $\frac{9}{8}$ : $\frac{-45}{24}$
= $\frac{-3}{5}$
c) $\frac{-5}{7}$ .$\frac{2}{11}$ + $\frac{-5}{7}$. $\frac{9}{11}$ +1 . $\frac{5}{7}$
=$\frac{-5}{7}$ .($\frac{2}{11}$+ $\frac{9}{11}$) + $\frac{5}{7}$
= $\frac{-5}{7}$ . 1 + $\frac{5}{7}$
=0
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