Answer:
4/5
Step-by-step explanation:
The purple paint is split into 16+3+1=20 parts: 16 parts of white, 3 parts of blue, and 1 part of red. Thus, in one gallon of purple paint, 16 out of the total 20 parts are white paint, so there are 16/20 x 1 gallon = 4/5 gallons of white paint in one gallon of purple paint.