Răspuns: 67 pasari
Explicație pas cu pas:
8 gaste
Plan
1) Cate rate are bunica ?
4 × 8 = 32 rate
2) Cate curci are bunica ?
32 - 25 = 7 curci
3) cate gaini are bunica ?
4 × 7 = 28 gaini
4) Cate pasari are bunica in total ?
8 gaste + 32 rate + 7 curci + 28 gaini = 75 pasari
5) Cate pasari i-au ramas, daca a vandut cate 2 pasari din fiecare specie?
75 - 2 × 4 = 75 - 8 = 67 pasari i-au ramas
sau:
( 8 - 2 ) + ( 32 - 2) + ( 7 - 2 ) + ( 28 - 2) = 6 + 30 + 5 + 26 = 67 pasari