Câu 4. Tìm x, biết:
a) $x + \frac{3}{5}=\frac{2}{3}$
$x = \frac{2}{3} - \frac{3}{5}$
$x = \frac{1}{15} $
b) $\frac{3}{7} - x =\frac{2}{5}$
$x =\frac{3}{7} - \frac{2}{5}$
$x =\frac{1}{35}$
c) $\frac{4}{9} - \frac{2}{3} .x= \frac{1}{3}$
$\frac{2}{3} x = \frac{4}{9} -\frac{1}{3}$
$\frac{2}{3} x = \frac{4}{9}$
$\frac{2}{3} x = \frac{4}{9}$
$x = \frac{4}{9} : \frac{2}{3}$
$x = \frac{2}{3} $
d) $\frac{3}{10} x- 1\frac{1}{2}= \frac{-2}{7} : \frac{5}{14} $
$\frac{3}{10} . x - \frac{3}{2} = \frac{-4}{5}$
$\frac{3}{10} .x = \frac{-4}{5} + \frac{3}{2}$
$\frac{3}{10} x = \frac{7}{10}$
$x = \frac{7}{3}$