A=500+10x+y+100x+30+y+100x+10y+7=210x+12y+537, care se divide la 3 pt ca 210,12 si 537 se divid la 3
b)B=10x+y+10y+z+10z+x=11(x+y+z) care se divide la 11
c)C=100x+10y+2+100y+10z+3+100z+10t+4+100t+10x+1=110x+110y+110z+10 care se divide la 5, pt ca 110 si 10 se divid la 5