M3=(0,3,6,9,12,15,18,21,24,27,30,33,36,39,42,45,48,51,54,57,60,63 etc) M7=(0,7,14,21,28,35,42,49,56,63,70 etc) M21=(0,21,42,63,86 etc) A intersecta=Se iau nr comune. M3 intersectat cu M7=M21 M3 intersectat cu M7=21 si 63 Din nr de mai sus... Cuplacere!!