Question 64839
Let x=number of liters of 37% iodine
Then 25-x=number of liters of 12% iodine

Now we know that the amount of pure iodine in the 37% solution (.37)(x) plus the amount of pure iodine in the 12% solution .12(25-x) must equal the amount of pure iodine in the final solution (25)(.16) so our equation to solve:

.37x+.12(25-x)=25(.16) simplifying we get:

.37x-.12x+3=4 collecting like terms we have:
.25x=4-3 or
.25x=1
x=4 liters of the 37% solution
25-x=25-4=21 liters of 12% solution

ck

.37(4)+.12(25-4)=25(.16)
1.48+2.52=4
4=4

Hope this helps.  Happy holidays.-----ptaylor