Question

Petru si Iulian au construit impreuna 21 de cuburi de zapada.Iulian a construit cu 3 cuburi mai putine decat Petru.Cate cuburi a construit fiecare?

Answer 1

p+i=21
i=p-3
p+p-3=21
2p=21+3
2p=14
p=24:2
p=12
i=12-3
i=9

Answer 2

P+I=21 cuburi
I=P-3
P-3+P=21 cuburi
2P-3=21 cuburi
2P=21+3
2P=24 cuburi
P=24:2
P=12(cuburi a construit Petru)
I=12-3
I=9(cuburi a construit Iulian)