Question

mihai si david au impreuna 55 cartonase, mihai si radu 77, iar david si radu 90. cate cartonase are fiecare copil?

Answer 1

M+D=55
M+R=77
D+R=90
2M+2D+2R=222
M+D+R=111
R=111-55=56
D=111-77=34
M=111-90=21