What is the present age of Aman, if after $20$ years, his age will be $7$ times his age $10$ years back?

The correct option is A $15$ years
Let present age of Aman be $x.$
Then, his age before $10$ years $=x-10$
and his age after $20$ years $=x+20$
We are given that, his age after $20$ years $(x+20)$ is $7$ times his age $10$ years back $(x-10)$
Therefore, $(x+20)=7(x-10)$
$\Rightarrow x+20=7x-70$
$\Rightarrow 6x=90$
$\therefore x=15$ years
Hence, the present age of Aman is $15$ years.