a-tatăl
b-mama
c=d=e fii gemeni
a+b+c+d+e=99
a+b=72
a=12+b
12+b+b=72
2×b+12=72
2×b=72-12
2×b=60
b=60:2
b=30 ( 30 ani are mama)
a=12+b
a=12+30
a=42 ( 42 ani are tata)
c+d+e=99-a+b
c+d+e=99-72
c+d+e=27
c=d=e=27:3
c=9
d=9
e=9 ( gemenii au cate 9 ani fiecare )
proba
42+30+9+9+9=72+27=99 (Adevarat )