Let n and d represent the numerator and denominator of the fraction.
.. (n +1)/(d +1) = 4/5
.. (n -5)/(d -5) = 1/2
Eliminating fractions from these equations gives
.. 5(n +1) = 4(d +1)
.. 2(n -5) = (d -5)
Subtracting the first equation from 4 times the second gives
.. 4(2(n -5)) -(5(n +1)) = 4(d -5) -(4(d +1))
.. 8n -40 -5n -5 = 4d -20 -4d -4
.. 3n = 21
.. n = 7
.. 2(7 -5) = d -5
.. 9 = d
The fraction is 7/9.
.. (n +1)/(d +1) = 4/5
.. (n -5)/(d -5) = 1/2
Eliminating fractions from these equations gives
.. 5(n +1) = 4(d +1)
.. 2(n -5) = (d -5)
Subtracting the first equation from 4 times the second gives
.. 4(2(n -5)) -(5(n +1)) = 4(d -5) -(4(d +1))
.. 8n -40 -5n -5 = 4d -20 -4d -4
.. 3n = 21
.. n = 7
.. 2(7 -5) = d -5
.. 9 = d
The fraction is 7/9.