The sequence of integers in each of the two rows of squares and in each of the two columns of squares form four separate arithmetic sequences. What is the least positive integer value for N?

87 75, 68, 61, 54, 47, 40, 33, 26 63 28 51 16 39, 32, 25, 18, 11, 4

The rule is -12 as a common difference for "down"

The rule is -7 as a common difference for "across"

Thank you so much! I understand it now!