Question 723073
The +1 equation gives {{{(a+1)/(b+1)=3/5}}}, simplifying to {{{5a-3b=-2}}}.

The -1 equation gives {{{(a-1)/(b-1)=5/9}}}, simplifying to {{{9a-5b=4}}}.


You could solve both of those for a, equate the expressions and solve for b.  Then substitute for b in either of the initial equations and find a.


ANSWER FOUND:  {{{a=11}}} and {{{b=19}}}.