Bro just go on Symbolab and use the calculator
Here is how I completed the problem:
I started by creating a ratio:

<em>Where 'x' is the desired amount of the 18% solution of sulfuric acid.
</em>From here, I solved for 'x':
<em>
</em>







∴You will need to add 1080ml of 18% Sulfuric Acid in order to obtain a 15% solution.
A. 48 = 12 + 20 + x
If you use this equation then you can do 12 + 20 = 32 and then you can do 48 - 32 = 16 so x = 16