Răspuns :
18+15+10=43
58-43=15
15:3=5
PRIMA ARE 18+5=23
A DOUA 15+5=20
A TRIA 10+5=15
23+20+15=58
58-43=15
15:3=5
PRIMA ARE 18+5=23
A DOUA 15+5=20
A TRIA 10+5=15
23+20+15=58
fie x ani, peroada de virsta care a trecut pina acum
I are 18+x
II are 15+x
III are 10+x
alcatui ecuatia 18+x+15+x+10+x=58
43+3x=58
3x=58-43
3x=15
x=5(ani) au trecut de atunci
I sora are 5+18=23
II sora 5+15=20 ani
III sora 5+10=15 ani
Verificare 23+20+15=58 ani au toate trei impreuna acum
I are 18+x
II are 15+x
III are 10+x
alcatui ecuatia 18+x+15+x+10+x=58
43+3x=58
3x=58-43
3x=15
x=5(ani) au trecut de atunci
I sora are 5+18=23
II sora 5+15=20 ani
III sora 5+10=15 ani
Verificare 23+20+15=58 ani au toate trei impreuna acum