Câu 3:
a. 40% - x = -2$\frac{2}{5}$
$\frac{2}{5}$ - x = -2$\frac{2}{5}$
x = $\frac{2}{5}$ - (-2$\frac{2}{5}$)
x = $\frac{2}{5}$ + 2$\frac{2}{5}$
x = 2$\frac{4}{5}$
b. ($\frac{x}{-5}$ + $\frac{2}{3}$) : 2$\frac{1}{5}$ - 1,4.$\frac{15}{49}$ = $\frac{|-5|}{21}$
($\frac{x}{-5}$ + $\frac{2}{3}$) : $\frac{11}{5}$ - $\frac{7}{5}$ .$\frac{15}{49}$ = $\frac{5}{21}$
($\frac{x}{-5}$ + $\frac{2}{3}$) : $\frac{11}{5}$ - $\frac{1}{1}$ .$\frac{3}{7}$ = $\frac{5}{21}$
($\frac{x}{-5}$ + $\frac{2}{3}$) : $\frac{11}{5}$ - $\frac{3}{7}$ = $\frac{5}{21}$
($\frac{x}{-5}$ + $\frac{2}{3}$) : $\frac{11}{5}$ = $\frac{5}{21}$ + $\frac{3}{7}$
($\frac{x}{-5}$ + $\frac{2}{3}$) : $\frac{11}{5}$ = $\frac{5}{21}$ + $\frac{9}{21}$
($\frac{x}{-5}$ + $\frac{2}{3}$) : $\frac{11}{5}$ = $\frac{2}{3}$
$\frac{x}{-5}$ + $\frac{2}{3}$ = $\frac{2}{3}$.$\frac{11}{5}$
$\frac{x}{-5}$ + $\frac{2}{3}$ = $\frac{22}{15}$
$\frac{x}{-5}$ = $\frac{22}{15}$ - $\frac{2}{3}$
$\frac{x}{-5}$ = $\frac{22}{15}$ - $\frac{10}{15}$
$\frac{x}{-5}$ = $\frac{12}{15}$
$\frac{x}{-5}$ = $\frac{4}{5}$
$\frac{x}{-5}$ = $\frac{-4}{-5}$
x = -4
