Question 288305
f=10a+b,
s=10b+a,
20<=f-s<=30
20 and 30 are not between 20 and 30
so it must be 26 or 27
It is 27.
a = 9-n,   b = 6-n,   f = 96-11 n,   s = 69-11 n,   n element Z,   n>=0
let n=1
a=8; b=5
possible ages for father and son
85-58=27
96-69=27
74-47=27
63-36=27
52-25=27
41-14=27
30-3=27

b=a-3
f=11a-3
s=11a-30