Tìm x, biết:

a) $\frac{3}{4} + \frac{1}{9} / x = 0.5$ suy ra $\frac{1}{9} / x = \frac{1}{2} - \frac{3}{4}$ nên $x = \frac{1}{9} / (\frac{- 1}{4}) = \frac{- 4}{9}$

b) $\frac{3}{4} - (x - \frac{2}{3}) = 1 \frac{1}{3}$ suy ra $x = \frac{2}{3} - \frac{4}{3} + \frac{3}{4} = \frac{1}{12}$

c) $(\frac{5}{7} - x) \times \frac{11}{15} = \frac{- 22}{45}$ suy ra $\frac{5}{7} - x = (\frac{- 22}{45}) / \frac{11}{15}$ nên $x = \frac{29}{21}$

d) $(2.5 x - \frac{4}{7}) / \frac{8}{21} = - 1.5$ suy ra $2.5 x - \frac{4}{7} = (\frac{- 3}{2}) \times \frac{8}{21}$ nên x=0