numărul e ab, suma e a+b
Scriem ab:(a+b)=c1, r=13 => a+b>13, a<10, b<10
ab:c1=c2, r=3 => c1>3
Din prima relatie obtinem:
a+b=14 => ab= (49, 58,67,76,85,94)
a+b=15 => ab = (59, 68,77,86,59)
a+b=16 => ab= (78,88,97)
a+b=17=> ab= (89,98)
a+b=18=> ab= (99)
98:17=5, r=13
98:5=19, r=3
