8/9=4/8+4/8;4/12+5/12=9/12....7/4+5/12=12/12...astea ca suma.....la ex 2 faci la fel dar scadere..
ai aceasi cifra la fractie.......probl 4..
din 900 kg ...scazi prima zi,adica jumatate ....900-450 =450 kg.....a doua zi..... 450 -150=300 kg.......900-750=150 kg.....succes
