You need to strengthen a 19% alcohol solution with pure alcohol solution to obtain 40% solution. how much pure alcohol should you add to 100 milliliters of the 19% solution. can anyone solve this

Let x be the number of mm of pure alcohol to be added:

I will add the mm to express the volume in mm
100mm.(19%) + (100%).x mL = (100 mL+x mL).(40%).
Now right again without the %
100.(0.19) + x.(1) = (100+x).(0.4)

19 + x = = 40 + 04x
x - 0.4x = 40 - 19
0.6 x = 21
x = 21/0.6  and x = 35 mL. This te quantity of pure alcohol should to be added to get a solution at 40%.

Ithink the answer is c just trying to others