3-\frac{2}{5}=2\frac{3}{5}
3-\frac{2}{5}=2\frac{5}{5}-\frac{2}{5}=2\frac{3}{5}
8-\frac{23}{25}=7\frac{2}{25}
wyjasnienie
8=7\frac{25}{25}
stąd
7\frac{25}{25}-\frac{23}{25}=7\frac{2}{25}
7-4\frac{2}{25}=2\frac{23}{25}
25-17\frac{3}{5}=24\frac{5}{5}-17\frac{3}{5}=7\frac{2}{5}