Question 1007657
Let x be the amount of 3% solution.
Thus 50-x is the amount  of 25% solution.
The set up looks like this:
.03x + .25(50-x) = .20(50)
.03x + 12.5 - .25x = 10
-.22x = -2.5
x = 2.5/.22 = 11.36 ml of 3% solution