(15(.17)+.29x)/(15+x)=.23
2.55+.29x=3.45+.23x
.06x=.9
x=15
So 15L of the 29% solution was added to the 15L of 17% solution to make
30L of 23% solution.
4/6=2/3
9/12=3/4
2/3 <3/4