correct answer is: a) 5

Explanation

Let the number which will add is = x
According to the question,
\left(9+x\right):\left(16+x\right)=2:3
\therefore \large\frac{9\ +\ x}{16\ +\ x}\ \normalsize=\ \large\frac{2}{3}
\therefore3\left(9+x\right)\ =\ 2\left(16+x\right)
\therefore\ 27\ +\ 3x\ =\ 32\ +\ 2x
\therefore\ 3x\ -\ 2x\ =\ 32\ -\ 27
\therefore x\ =\ 5
So, the number is 5 which added to each term of the ratio 9 : 16 to make the ratio 2 : 3.
Ans: The number is 5.