Question 560385
<pre>
t = tens digit of N
u = units digit of N
10t + u = N
10u + t = K

                N - K > 18  
(10t + u) - (10u + t) > 18
    10t + u - 10u - t > 18
              9t - 9u > 18
                t - u > 2   
                    t > u + 2 

Since t < 10, it must be that u < 7

Since N is odd, the units digit is u = 1,3, or 5

If u = 1, t > 3, so N = 41,51,61,71,81,91
If u = 3, t > 5, so N = 63,73,83,93
If u = 5, t > 7, so N = 85,95

Edwin</pre>