Răspuns :
a : 8 = a - 63 <=> a = 8a - 504 => 8a - a = 504 => 7a = 504 =>
a = 504 :7 => a = 72
Verificare : 72 :8 = 9 = 72 - 63 = 9 ; corect
a = 504 :7 => a = 72
Verificare : 72 :8 = 9 = 72 - 63 = 9 ; corect