To find the amount of red paint to add to the 16 fl oz of white paint, you can set up a proportion and then use cross products to solve for the missing amount of red paint.
red 2 x
white 7 = 16 fl oz
16 x 2 = 7x
32 = 7x
7 7
x = 4 4/7 (approximately 4.6 fl oz)
You will need approximately 4.6 fl oz (or exactly 4 4/7 fl oz) of red paint.