Giải bài 5 trang 30 toán 7 tập 1 cánh diều

a. $x + (- \frac{2}{9}) = \frac{- 7}{12}$

$x = \frac{- 7}{12} + \frac{2}{9}$

$x = \frac{- 21}{36} + \frac{8}{36}$

$x = \frac{- 13}{26}$

b. $(- 0, 1) - x = \frac{- 7}{6}$

$\frac{- 1}{10} - x = \frac{- 7}{6}$

$x = \frac{- 1}{10} + \frac{7}{6}$

$x = \frac{- 3}{30} + \frac{35}{30}$

$x = \frac{32}{30} = \frac{16}{15}$

c. $(- 0, 12) . (x - \frac{9}{10}) = - 1, 2$

$\frac{- 3}{25} . (x - \frac{9}{10}) = \frac{- 6}{5}$

$x - \frac{9}{10} = \frac{- 6}{5} : (\frac{- 3}{25})$

$x - \frac{9}{10} = \frac{- 6}{5} . \frac{- 25}{3}$

$x - \frac{9}{10} = 10$

$x = 10 + \frac{9}{10} = \frac{109}{10}$

d. $(x - \frac{3}{5}) : \frac{- 1}{3} = 0, 4$

$(x - \frac{3}{5}) = \frac{2}{5} . \frac{- 1}{3}$

$x - \frac{3}{5} = \frac{- 2}{15} . \frac{- 1}{3}$

$x - \frac{3}{5} = \frac{- 2}{15}$

$x = \frac{- 2}{15} + \frac{3}{5}$

$x = \frac{7}{15}$