Question 1149312
adding x ml 19% water
start with 7.10 ml pure water (0.71*10)and add 0.19x ml, which is 7.10 +0.19x ml
final is (10+x)ml*0.32=3.2 ml+0.32x ml

Those two are equal, so 3.2+0.32x=7.10+0.19x
0.13x=3.9
x=30 ml

check started with 7.10 ml pure water and ended with 7.1 +5.7 (30*.19)=12.8 ml
also have 40 ml of .32 pure water which is also 12.8 ml