x - ilość zebranej makulatury
x=\frac{2}{5}x+\frac{3}{14}x+\frac{2}{7}x+49
x=\frac{2}{5}x+\frac{3}{14}x+\frac{4}{14}x+49
x=\frac{2}{5}x+\frac{7}{14}x+49
x=\frac{28}{70}x+\frac{35}{70}x+49
x=\frac{63}{70}x+49
x-\frac{63}{70}x=49
\frac{7}{70}x=49 /:7
\frac{1}{10}x=49 /*10
x=490 tyle zebrali razem
\frac{2}{5}*490=\frac{980}{5}=196 (Va)
\frac{3}{14}*490=\frac{1470}{14}=105 (Vb)
\frac{2}{7}*490=\frac{980}{7}=140 (Vc)