Câu 2.
a) $\frac{5}{23}+\frac{7}{17}+0,25-\frac{5}{23}+\frac{10}{17}$
= $\frac{5}{23}+\frac{7}{17}+\frac{1}{4}-\frac{5}{23}+\frac{10}{17}$
= $\frac{5}{23} -\frac{5}{23} + \frac{7}{17} +\frac{10}{17} +\frac{1}{4}$
= 0 + 1 + $\frac{1}{4}$
= $\frac{5}{4}$
b) $\frac{3}{7}.2\frac{2}{3}-\frac{3}{7}.1\frac{1}{2}$
= $\frac{3}{7}. [\frac{8}{3} -\frac{3}{2}]$
= $\frac{3}{7}. \frac{7}{6}$
= $\frac{1}{2}$
c) $13\frac{1}{4}:\left ( \frac{-4}{7} \right )-17\frac{1}{4}:\left (\frac{-4}{7} \right )$
= $(13\frac{1}{4} - 17\frac{1}{4}) :\left ( \frac{-4}{7} \right )$
= $-4 : \left ( \frac{-4}{7} \right )$
= 7
d) $\frac{100}{123}:\left( \frac{3}{4}+\frac{7}{12} \right)+\frac{23}{123}:\left( \frac{9}{5}-\frac{7}{15} \right)$
= $\frac{100}{123}:\frac{4}{3}+\frac{23}{123}:\frac{4}{3}$
= $\left( \frac{100}{123}+\frac{23}{123} \right).\frac{3}{4}$
$=\frac{3}{4}$