Răspuns :
a+b+c=300.
a=b+20.
c=3b.
Inlocuim:b+20+b+3b=300.
5b+20=300.
5b=280=>b=56.
a=56+20=76.
c=3x56=...
a-primul nr.
b-al doi lea nr.
c-al trei lea nr.
a+b+c=300
a+20=b
c=bx3
a+a+20+bx2=300
2a+20+(a+20)x2=300
2a+20+2a+40=300
4a+60=300
4a=240
a=60
b=60+20=80
c=80x3=240
b-al doi lea nr.
c-al trei lea nr.
a+b+c=300
a+20=b
c=bx3
a+a+20+bx2=300
2a+20+(a+20)x2=300
2a+20+2a+40=300
4a+60=300
4a=240
a=60
b=60+20=80
c=80x3=240