Hi, I am stuck on a puzzle, don't have too many boxes filled in and can't go further. I don't usually get stuck this early, so am puzzled. Could someone please tell me what logic they used to move forward? Thanks very much in advance!
6X8 XXX 31X
3X9 X81 XX4
145 X32 X78
X6X 1X9 XXX
XXX XXX XXX
XX7 2X3 X5X
951 X2X X36
786 31X 2XX
234 XXX X81