Question 520053
 Anil and Sunil are two friends. The sum of their ages is 35 years. Anil is twice as old as Sunil was when Anil was as old as Sunil is now. What is the present age of Anil?

let a be Abil's age now and s be Sunil's age now. let y be Sunil's age when Anil was s (as old as Sunil is now), x a number.

the sum of their ages is 35, means a + s=35  (1)
x years ago, Abil was s. so s + x=a    
x years ago, ( when Abil was s) Sunil was y. so y + x= s        
                                                y= s - x

from the data, we know that when Anil's age now is twice y.
so a= 2(s -x)    and a= s+x
 so 2s -2x= s + x
   s = 3x
 
a= s + x= 3x + x= 4x.

by the equation (1) in term of x, we have
 a +s = 35
 4x + 3x= 35
7x = 35
 x=5.

   a= 4x = 4*5 = 20
   s= 3x = 3*5 = 15
 so now,Anil is 20 years old.

to check: Anil is 20, which is 2 times 10( age that Sunil was  when Anil was 15).