abc : bc = 6 rest 5
abc = 6 x bc +5
a x 100 + bc = 6 x bc +5
100 a -5 = 6 bc - bc
100 a -5 = 5 bc
5( 20 a -1 ) = 5 bc / :5
20 a -1 = bc
daca a=1⇒ bc= 20-1=19⇒ abc= 119
daca a=2⇒ bc= 40-1=39⇒ abc= 239
daca a=3⇒ bc= 60-1 =59⇒ abc= 359
daca a=4⇒ bc= 80-1=79⇒ abc = 479
daca a=5⇒ bc= 100-1= 99⇒ abc= 599