Răspuns:
a) 100a+10b+1+200+10a+b+100a+10b+0=684
210a+21b+201=684
210a+21b=483 | : 21
10a+b=23
ab = 23 ( in baza 10)
b)1000a+100b+10c+0+1000+100a+10b+c+1000a+100b+10c+3+2000+100a+10b+c=5709
2200a+220b+22c=2706 | : 22
100a+10b+c=123
abc=123( in baza 10)
c)100a+10b+c+5000+100a+10b+c+1000a+100b+10c=7532
1200a+120b+12c= 7532-5000=2532 | : 12
abc=211 ( baza 10)
d) 3 7 5 8 +
1 6 7 4
= 5 4 3 2