Question 865742
Easier to ask how much water is needed to make 4.5% from 32 ml of 12%.  That is a high enough concentration that density should be needed, UNLESS percent is in mass per volume.


Let u = how much ml of water to add;
ASSUMING percents are mass per volume.


{{{highlight_green(32*12/(u+32)=4.5)}}}.
Solve for u.