Given:
Sarvi is creating an acid solution.
He has 5 liters of a 4% acid solution
He wants to create a 7% acid solution by adding in a 9% solution.
We will find How of the 9% solution should he add in.
Let the number of liters should be added = x
The total liters of the 7% acid solution = 5 + x
So, we can write the following equation

So, the answer will be option 3