To solve this problem you must aplpy the proccedure below:
1. You have that the lab technician mixed 520 ml solution of water and alcohol and 3% is alcohol.
2. ml of alcohol:
520 ml----100%
x----3%
x=3x520/100
x=15.6 ml
3. ml of water:
y=520 ml-15.6 ml
y=504.4 ml
14. Therefore, as you can see, the answer is:
15.6 ml of alcohol and 504.4 ml of water were used by the lab technician.