Question 889910
Present age of john = 9
Present age of his father = 32
After n years,john's age is half as that of his father.
     9+n=1/2×(32+n)
    18+2n=32+n
   2n-n=32-18    
      n=14
Check: 
      9+14=23
      32+14=46
     23=1/2×46
Therefore n = 14