Răspuns :
fie x,3x nr necunoscute
avem ecuatia:x+3x=40
4x=40
x=40:4
x=10
raspuns:10,30
verificare:30+10=40
avem ecuatia:x+3x=40
4x=40
x=40:4
x=10
raspuns:10,30
verificare:30+10=40
a+b=40
a=bx3
bx3+b=40
bx4=40
b=40:4
b=10
a=10x3
a=30
proba:30+10=40
a=bx3
bx3+b=40
bx4=40
b=40:4
b=10
a=10x3
a=30
proba:30+10=40