Câu 1 :
a) $\frac{-63}{81}$ = $\frac{-7}{9}$
b) $\frac{5.6}{9.35}$ = $\frac{1.2}{3.7}$ = $\frac{2}{21}$
c) $\frac{13.2-2.6}{4.5.6}$ = $\frac{14}{120}$ = $\frac{7}{60}$
Câu 2 :
a)$\frac{1}{3}$ - $\frac{5}{4}$ . $\frac{4}{15}$ = $\frac{1}{3}$ - $\frac{1}{3}$ = $\frac{0}{3}$
b) $\frac{-3}{5}$ + ($\frac{-2}{5}$ + 2) = $\frac{-3}{5}$ + $\frac{-2}{5}$ + 2 = $\frac{-5}{5}$ + 2 = (-1) + 2 = 1
c) $\frac{-5}{7}$ . $\frac{2}{11}$ + $\frac{-5}{7}$ . $\frac{9}{11}$ + 1$\frac{5}{7}$ = $\frac{-5}{7}$ . ($\frac{2}{11}$ + $\frac{9}{11}$) + $\frac{12}{7}$ = $\frac{-5}{7}$ . 1 + $\frac{12}{7}$ = $\frac{-5}{7}$ + $\frac{12}{7}$ = $\frac{7}{7}$ = 1
Câu 3 :
a) 5$\frac{4}{7}$ : x = 13
=> $\frac{39}{7}$ : x = 13
=> x = $\frac{39}{7}$ : 13
=> x = $\frac{3}{7}$
b) $\frac{2}{3}$ + x = -45%
=> $\frac{2}{3}$ + x = $\frac{-9}{20}$
=> x = $\frac{-9}{20}$ - $\frac{2}{3}$
=> x = $\frac{-67}{60}$
c) (4,5 + $\frac{3}{4}$x) : $\frac{8}{3}$ = $\frac{9}{8}$
=> ($\frac{9}{2}$ + $\frac{3}{4}$x) = $\frac{9}{8}$ . $\frac{8}{3}$
=> $\frac{9}{2}$ + $\frac{3}{4}$x = $\frac{3}{1}$
=> $\frac{3}{4}$x = $\frac{3}{1}$ - $\frac{9}{2}$
=> $\frac{3}{4}$x = $\frac{-3}{2}$
=> x = $\frac{-3}{2}$ : $\frac{3}{4}$
=> x = $\frac{-2}{1}$ = -2
