notam a,b,c cantitatile de grau din cele 3 magazii
a+b+c=300t
a+45t=b-(45t+27t)=c+27t
=> a=b-72t-45t
a=b-117t
c=b-72t-27t
c=b-99t
a+b+c=(b-117t)+b+(b-99t)=300t
3b-216t=300t
3b=516t
b=172t
a=172t-117t
a=55t
c=172t-99t
c=73t
verificare: 55t+172t+73t=300t
55t+45t=172t-(45t+27t)=73t+27t (A)
