Răspuns :
ab + ac + ad = 2005
a(b + c + d) = 2005
b + c + d = 401
a * 401 = 2005
a = 2005/401
a = 5
a(b + c + d) = 2005
b + c + d = 401
a * 401 = 2005
a = 2005/401
a = 5