Cách làm cho bạn:
Ta có:
a) $\frac{45}{4}−(2\frac{5}{7}+5,25)$;
$=\frac{45}{4}−(\frac{19}{7}+2\frac{1}{4})$
=$\frac{45}{4}−\frac{223}{28}$
=$\frac{23}{7}$
b) $\frac{5}{9}:2,4 − \frac{41}{9}: 2,4$;
= $(\frac{5}{9}−\frac{41}{9})/2,4$
= $(-4) : 2,4 = \frac{−5}{3}$
c) $(−\frac{3}{4}+\frac{5}{13}).\frac{7}{2}−(\frac{9}{4}−\frac{8}{13}).\frac{7}{2}$
= $(−\frac{3}{4}+\frac{5}{13}−\frac{9}{4}+\frac{8}{13}).\frac{7}{2}$
= $(-2) . \frac{7}{2}$
$= -7$
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