My precedent post has a big flaw, which I noticed after the last posts of Charlie and Harry, so I'm correcting it here.
C=5*(F32)/9
For F congruent 5 (mod 9) C will be an integer (congruent to mod 5).
C/F will be integer when C higher or equal than F (or if C=0). For F values, this occurs in the interval: (40, 11). There are six possible values of F mod compliant in that interval: (40, 31, 22, 13, 4, 5)
F=40 C=40 N=1
F=31 C=35 N not integer
F=22 C=30 N=not integer
F=13 C=25 N=not integer
F=4 C=20 N=5
F=5 C=15 N=3
and the solution for C=0 (F=32, N=0)
So N,X = (1,40) (5,20) (3,15) (0,0)
Charlie points out two other solutions admitting that Celsius degrees and N are integers but not necessarily the Farenheit degrees. It could be.
But really the formula of the puzzle is not precise as X° is symbol for both Celsius degrees and Farenheit degrees. All of us have used X° as Celsius, but we could have used X° for Farenheit, and could had given our answers also as (1,40) (5,4) (3,5) (0,0), referring the numbers to N and Farenheit degrees. It would have been also a valid answer.
So perhaps, as it is, (N, X) integers stands for N, F, C integers, but if X stands only for C, which is in the logic of the puzzle, the set of "simple" F solutions can be enlarged with other two values.
Edited on June 23, 2016, 6:30 am

Posted by armando
on 20160623 04:14:34 