Place the numbers 1-9 in the boxes so that the difference of each pair of numbers joined by a line is at least three. The number 8 has already been placed.
(In reply to re: solution by reasoning
by ed bottemiller)
I wrote you without having the diagram before my eyes
the passage "..I get H as calling for a member of the R set, i.e. 1,2, or 9 -8 being placed in A by problem's initial conditions.
Assigning 1 to H, D could be either 4 or 5..."..
should read: C could be either 4 or 5
S O R R Y