Question

Mihai si David au impreuna 55 cartonase,Mihai si Radu au impreuna 77 de cartonase,iar David si Radu 90 de cartonase.

Cate cartonase are fiecare copil?

Answer 1

m+d=55 |
m+r=77 | +
d+r=90 |
------------
2m+2d+2r=222
m+d+r=111
55+r=111
r=56

77+d=111
d=35

m+d+r=111
m+90=111
m=21