Notam cu a,b si c cele trei numere .
a+b+c=900
b=al doilea numar
b=3a
c=al treilea numar
c=b+25 ,adica
c=3a+25
Inlocuim obtinem
a+3a+3a+25=900
7a=900-25
7a=875
a=125
si b=3*125=375
b=375
c=3*125+25=400
a=125 b=375 c=400
facem si proba
125+375+400=900