CBSE Class 10 Answered

  Let the numerator be x and the denominator be y.   the fraction is  x/ y

  numerator is 4 less than the denominator ie. x  =  y - 4.  ie  x - y = - 4.  --------  (1)

 numerator decresed by 2  is x - 2 and denominator increased by 1 is y + 1

        y + 1 = 8 ( x - 2 )   ie   8 x - y  = 17  ----------  ( 2 )

 solving equation 1 and 2by substitution method

      8 ( - 4 + y ) - y = 17.  ie  -32 + 8y - y = 17,         7y =49         y = 7

    x - 7 = -4  ,        x = 3

   the fraction is  3 / 7

    second answer

     Let father's age be x  and son's age be y

   according to question  x = 3y + 3 .   ie.  x - 3y = 3  -----------   ( 1 )

3 yrs later father's age is x +3 and son's age is y + 3

  according nto question  x + 3 = 2 ( y + 3 ) + 10.   ie   x - 2y = 13 ---------   ( 2 )

  solving both equation by substitution method    

    3 + 3y - 2y = 13.     ie   y = 10  and x = 33

  father's age  33 yrs and son's age 10 yrs