notam : cuburi = a , sfere=b , cuboide=c
stim ca: a+b+c=49 , c=49-a-b
a+b=38
a+c=36 => a+49-a-b=36 49-b=36 -b=36-49 -b=-13 si obtinem b=13(imparti cu -1)
Deci pana acuma sunt 13 sfere. Daca avem sferele putem inlocui in a+b=38 : a+13=38 -> a=38-13=25 cuburi
25+c=36 => c=36-25=11
PROBA: a+b+c=25+13+11=38+11=49