[tex]1)~x\in\{11,12,...,20\}[/tex]
Aceste numere dau resturile: 2, 0, 1, 2, 0, 1, 2, 0, 1 si 2
2+0+1+2+0+1+2+0+1+2 = 2+1+2+1+2+1+2 = 11
2) a+b = 32
a:b = 6 rest 4
a = 6b+4
6b+4+b = 32
7b = 28
b = 4
a = 28
3) a-b = 5085
a:b = 5 rest 141
a = 5b+141
5b+141-b = 5085
4b = 4944
b = 1236
a = 6321