Question 941572
let present age of bob be x years
 bob's father =  3times bob's age
     = 3x
4 years ago, age of bob  = x-4
  4 years ago, age of father  = 3x-4
 4 years afo father's age = 34 times bob's age
   3x-4 =4(x-4)
  3x-4 = 4x-16
   16+3x-4= 4x
     12 +3x=4x
          12 = 4x-3x
      12 =x
Result: age of bob(x)= 12  years