like you said, "A number is divisible by 8 if the number formed by its last 3 digits is divisible by 8." so, we have to find the lowest possible number there is for 1A6, which would be 136 because 96 is divisibe by 8, and the smallest number that is divisible by both 8 and 10 is 40, so we add 40. then, we can repeat that process once more, and we get 136, and 176. there's no other numbers that have hundreds digit of 1, and units digit as 6 toher than those two, so 3+7=$\boxed{10}$
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