N and M are each 3-digit integers

N and M are each 3-digit integers. Each of the numbers 1, 2, 3, 7, 8 and 9 is a digit of either N or M. What is the smallest possible positive difference between N and M?

AQuA-RAT — Algebra Question Answering with Rationales (Ling et al., DeepMind, 2017) · train #87425