Let $a_1, a_2, a_3,\dots$ be an increasing arithmetic sequence of integers. If $a_4a_5 a_6 = 6$, what is $a_3a_7$?
Do you mean a4 + a5 + a6 = 6 ?
If so, I think that would be 1 + 2 + 3 = 6
which would make a3 = 0 and a7 = 4
if I understand the problem correctly.