Question 494254
If % is by weight, you will have to know the weight ratio.
So let's assume it's % by volume.
You have a gallon of stuff, 32% is HCL, so 68% is H20.
You are going to add x gallons H2O so that the result is 15% HCL.
HCL / Total.stuff = 15%
(.32 gal)/(1+x gal) = 0.15
32 = 15 + 15x
x = 17/15 = 1 2/15 gal