Question

banu is 20 years older than binu.in 5 years ,banu will be twice as old as binu .find their present age

Answer 1

Answer :
         Let Present age of Binu = x
         Therefore, Present age of Banu = x+20
     After 5 years,
         Age of Binu = x+5
         Age of Banu = (x+20)+5
                            = x+25
According to question ,
               x+25 = 2 (x+5)
              x+25 = 2x + 10
                 25 = 2x+10 - x
                 25 = x+10
                 25 - 10 =x
                15 = x
               or x= 15


Hence Present age of Binu = 15 years

  and Present age of BAnu = x+20
                                            = 15 + 20
                                            =35 Years !!

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Answer 2

Let the age of banu = x and 
Let the age of Binu = y.

Then A.T.Q

1.  x = 20 + y   ------------------------(1)

2. x + 5 = 2(y + 5)

x + 5 =  2y + 10 - ----------------------(2)

Putting the value of x in  (2)
20 + y + 5 = 2y + 10
y - 2y = 10 - 25
-y = -15
y= 15
Hence the age of Binu is 15 years. 
Now , for Banu age x= 20 + y
x = 20 + 15
x= 35

Hence the age of Banu is 35 years.