Din a*c=72
2)a=72:c
Din b*c=108
b=108:c
Inlocuin a si b in ........ 5a+3b=57
5*72:c + 3*108:c=57
360c+324c=57
684c=57
c=12
Atunci : a=72:12
a=6
si
b=108:12
b=9
Numerele a,b si c sunt egale cu 6,9 si respectiv12
1)ab in baza 10 : 4=c , r:3
ab=4c +3
Acum inlocuiesti pe c cu numerele 0,1,2,3,4,5,6,7,8,9
S1____ ab=0+3=3 Fals
S2____ ab=4+3=7 Fals
S3____ ab=8+3=11 Adevarat
S4____ ab=12+3=15 Adevarat
S5____ ab=16+3=19 Adevarat
S6____ ab= 20+3=23 Adevarat
S7____ ab= 24+3=27 Adevarat
S8____ ab=28+3=31 Adevarat
S9____ ab=32+3=35 Adevarat
S10___ ab=36+3=39 Adevarat
In concluzie ab=11,15,19,23,27,31,35,39 si c=3,4,5,6,7,8 si 9