[tex](0.8 - \frac{1}{5} ) \times ( \frac{4}{5} - 0.1) = (\frac{4}{5} - \frac{1}{5} ) \times ( \frac{8}{10} - \frac{1}{10} ) = \frac{3}{5} \times \frac{7}{10} = \frac{21}{50} = \frac{42}{100} = 0.42[/tex]
Czyli ułóżmy proporcję
[tex]7\% - 0.42 \\ 100\% - x \\ \\ x = \frac{0.42 \times 100}{7} = \frac{42}{7} = 6[/tex]
Ta liczba to 6
