Sorry, my posts are not going through for some reason.
Clarification: is the 1st question asking for m1+m3?
Otherwise m1+m2 = 3 and m1m2=6 is not possible.
My reckoning was:
N = 100a_1 + 10a_2+a_3 = 98a_1+7a_2 + (2a_1+3a_2+a_3)
But I really dont know what is meant by "smallest natural numbers" when we are talking of a triplet like this. In any case it is easy to prove that it does not hold for coefficients lesser than those given here.